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Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2019	Nov. 08, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-38600
Entity Registrant Name	TENABLE HOLDINGS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-5580846
Entity Address, Address Line One	7021 Columbia Gateway Drive
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Columbia
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21046
City Area Code	410
Local Phone Number	872-0555
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	TENB
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		98,187,608
Entity Central Index Key	0001660280
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Ex Transition Period	true

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 171,303	$ 165,116
Short-term investments	125,333	118,119
Accounts receivable (net of allowance for doubtful accounts of $557 and $188 at September 30, 2019 and December 31, 2018, respectively)	81,201	68,261
Deferred commissions	26,030	23,272
Prepaid expenses and other current assets	21,126	22,020
Total current assets	424,993	396,788
Property and equipment, net	18,525	11,348
Deferred commissions (net of current portion)	38,493	36,162
Operating lease right-of-use assets	40,346	8,504
Other assets	9,855	7,810
Total assets	532,212	460,612
Current liabilities:
Accounts payable	795	171
Accrued expenses	9,474	5,554
Accrued compensation	24,244	29,594
Deferred revenue	245,985	213,644
Operating lease liabilities	3,970	4,262
Other current liabilities	701	1,079
Total current liabilities	285,169	254,304
Deferred revenue (net of current portion)	83,390	76,259
Operating lease liabilities (net of current portion)	37,788	6,055
Other liabilities	2,677	2,231
Total liabilities	409,024	338,849
Stockholders’ equity:
Common stock (par value: $0.01; 500,000 shares authorized; 97,960 and 93,126 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively)	980	931
Additional paid-in capital	648,964	586,940
Accumulated other comprehensive income	60	0
Accumulated deficit	(526,816)	(466,108)
Total stockholders’ equity	123,188	121,763
Total liabilities and stockholders’ equity	$ 532,212	$ 460,612

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 557	$ 188
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	97,960,000	93,126,000
Common stock, shares outstanding (in shares)	97,960,000	93,126,000

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 91,852	$ 69,440	$ 257,537	$ 192,139
Cost of revenue	15,245	12,161	42,389	30,768
Gross profit	76,607	57,279	215,148	161,371
Operating expenses:
Sales and marketing	56,699	44,550	165,403	125,964
Research and development	20,763	20,553	64,396	55,529
General and administrative	17,472	13,272	48,595	32,868
Total operating expenses	94,934	78,375	278,394	214,361
Loss from operations	(18,327)	(21,096)	(63,246)	(52,990)
Interest income, net	1,527	894	4,677	845
Other expense, net	(240)	(185)	(576)	(605)
Loss before income taxes	(17,040)	(20,387)	(59,145)	(52,750)
Provision for income taxes	600	482	1,563	1,157
Net loss	(17,640)	(20,869)	(60,708)	(53,907)
Accretion of Series A and B redeemable convertible preferred stock	0	(55)	0	(434)
Net loss attributable to common stockholders	$ (17,640)	$ (20,924)	$ (60,708)	$ (54,341)
Net loss per share attributable to common stockholders, basic and diluted (in usd per share)	$ (0.18)	$ (0.28)	$ (0.64)	$ (1.34)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	96,709	74,261	95,433	40,688

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (17,640)	$ (20,869)	$ (60,708)	$ (53,907)
Other comprehensive (loss) income, net of tax:
Unrealized (losses) gains on available-for-sale securities	(20)	0	60	0
Other comprehensive (loss) income	(20)	0	60	0
Comprehensive loss	$ (17,660)	$ (20,869)	$ (60,648)	$ (53,907)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock
Balance (in shares) at Dec. 31, 2017						15,848	39,538
Balance at Dec. 31, 2017						$ 49,935	$ 227,800
Redeemable Convertible Preferred Stock [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock						$ 13	$ 421
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)						(15,848)	(39,538)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering						$ (49,948)	$ (228,221)
Balance (in shares) at Sep. 30, 2018						0	0
Balance at Sep. 30, 2018						$ 0	$ 0
Balance (in shares) at Dec. 31, 2017		24,472
Balance at Dec. 31, 2017	$ (371,665)	$ 246	$ 20,676	$ 0	$ (392,587)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock	(434)		(434)
Exercise of stock options (in shares)		654
Exercise of stock options	1,415	$ 6	1,409
Repurchase of common stock (in shares)		(7)
Repurchase of common stock	(75)	$ (1)	(74)
Stock-based compensation	14,259		14,259
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses (in shares)		12,535
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses	264,799	$ 125	264,674
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)		55,386
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	278,169	$ 554	277,615
Other comprehensive income	0
Net loss	(53,907)				(53,907)
Balance (in shares) at Sep. 30, 2018		93,040
Balance at Sep. 30, 2018	132,561	$ 930	578,125	0	(446,494)
Balance (in shares) at Jun. 30, 2018						15,848	39,538
Balance at Jun. 30, 2018						$ 49,946	$ 228,168
Redeemable Convertible Preferred Stock [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock						$ 2	$ 53
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)						(15,848)	(39,538)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering						$ (49,948)	$ (228,221)
Balance (in shares) at Sep. 30, 2018						0	0
Balance at Sep. 30, 2018						$ 0	$ 0
Balance (in shares) at Jun. 30, 2018		24,951
Balance at Jun. 30, 2018	(398,724)	$ 250	26,651	0	(425,625)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock	(55)		(55)
Exercise of stock options (in shares)		168
Exercise of stock options	405	$ 1	404
Stock-based compensation	8,836		8,836
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses (in shares)		12,535
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses	264,799	$ 125	264,674
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)		55,386
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	278,169	$ 554	277,615
Other comprehensive income	0
Net loss	(20,869)				(20,869)
Balance (in shares) at Sep. 30, 2018		93,040
Balance at Sep. 30, 2018	$ 132,561	$ 930	578,125	0	(446,494)
Balance (in shares) at Dec. 31, 2018						0	0
Balance at Dec. 31, 2018						$ 0	$ 0
Balance (in shares) at Sep. 30, 2019						0	0
Balance at Sep. 30, 2019						$ 0	$ 0
Balance (in shares) at Dec. 31, 2018	93,126	93,126
Balance at Dec. 31, 2018	$ 121,763	$ 931	586,940	0	(466,108)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Exercise of stock options (in shares)	3,625	3,625
Exercise of stock options	$ 15,448	$ 36	15,412
Vesting of restricted stock units (in shares)		432
Vesting of restricted stock units	0	$ 5	(5)
Issuance of common stock under employee stock purchase plan (in shares)		777
Issuance of common stock under employee stock purchase plan	15,129	$ 8	15,121
Stock-based compensation	31,496		31,496
Other comprehensive income	60			60
Net loss	$ (60,708)				(60,708)
Balance (in shares) at Sep. 30, 2019	97,960	97,960
Balance at Sep. 30, 2019	$ 123,188	$ 980	648,964	60	(526,816)
Balance (in shares) at Jun. 30, 2019						0	0
Balance at Jun. 30, 2019						$ 0	$ 0
Balance (in shares) at Sep. 30, 2019						0	0
Balance at Sep. 30, 2019						$ 0	$ 0
Balance (in shares) at Jun. 30, 2019		96,808
Balance at Jun. 30, 2019	120,959	$ 968	629,087	80	(509,176)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Exercise of stock options (in shares)		383
Exercise of stock options	2,721	$ 4	2,717
Vesting of restricted stock units (in shares)		431
Vesting of restricted stock units	0	$ 5	(5)
Issuance of common stock under employee stock purchase plan (in shares)		338
Issuance of common stock under employee stock purchase plan	6,550	$ 3	6,547
Stock-based compensation	10,618		10,618
Other comprehensive income	(20)			(20)
Net loss	$ (17,640)				(17,640)
Balance (in shares) at Sep. 30, 2019	97,960	97,960
Balance at Sep. 30, 2019	$ 123,188	$ 980	$ 648,964	$ 60	$ (526,816)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (60,708)	$ (53,907)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,604	4,580
Stock-based compensation	31,191	14,206
Other	(787)	771
Changes in operating assets and liabilities:
Accounts receivable	(13,309)	(8,190)
Prepaid expenses and other current assets	820	941
Deferred commissions	(5,089)	(2,708)
Other assets	(2,386)	315
Accounts payable and accrued expenses	3,892	1,930
Accrued compensation	(5,350)	1,252
Deferred revenue	39,472	39,880
Other current liabilities	(195)	(4)
Other liabilities	173	(71)
Net cash used in operating activities	(7,672)	(1,005)
Cash flows from investing activities:
Purchases of property and equipment	(10,262)	(4,140)
Purchases of short-term investments	(179,703)	(34,114)
Sales and maturities of short-term investments	174,485	0
Net cash used in investing activities	(15,480)	(38,254)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting discounts and commissions	0	268,531
Payments of costs related to initial public offering	0	(3,732)
Principal payments under finance lease obligations	(12)	(389)
Proceeds from stock issued in connection with the employee stock purchase plan	15,129	0
Proceeds from the exercise of stock options	15,448	1,415
Repurchases of common stock	0	(75)
Net cash provided by financing activities	30,565	265,750
Effect of exchange rate changes on cash and cash equivalents and restricted cash	(1,226)	(675)
Net increase in cash and cash equivalents and restricted cash	6,187	225,816
Cash and cash equivalents and restricted cash at beginning of period	165,378	27,472
Cash and cash equivalents and restricted cash at end of period	171,565	253,288
Supplemental disclosure of cash flow information:
Cash paid for interest	73	85
Cash paid for income taxes	1,507	920
Supplemental cash flow information related to leases:
Operating cash payments for operating leases	3,297	3,098
Operating cash payments for finance leases	5	29
Supplemental disclosure of non-cash investing and financing activities:
Asset retirement obligations	$ 121	$ 67

Business and Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Business and Summary of Significant Accounting Policies

Business Description

Tenable Holdings, Inc. (the “Company,” “we,” "us," or “our”) is a provider of Cyber Exposure solutions, which is a discipline for managing, measuring and comparing cybersecurity risk in the digital era. Our enterprise software platform enables broad visibility into an organization’s cyber exposure across the modern attack surface and deep insights that help organizations translate technical data into business insights to understand and reduce their cybersecurity risk.

Basis of Presentation

The accompanying consolidated financial statements include the accounts of Tenable Holdings, Inc. and our wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

The consolidated financial statements have been prepared in conformity with United States generally accepted accounting principles (“GAAP”) for interim financial information. The consolidated statements are unaudited and should be read in conjunction with the consolidated financial statements and related notes included in our 2018 Annual Report on Form 10-K ("10-K") filed with the Securities and Exchange Commission on March 1, 2019. The consolidated financial statements have been prepared on a basis consistent with the audited annual consolidated financial statements included in the 10-K and, in the opinion of management, include all adjustments of a normal recurring nature necessary to fairly state our financial position, our results of operations, and cash flows.

The results for the nine months ended September 30, 2019 are not necessarily indicative of the operating results expected for the year ending December 31, 2019 or any other future period.

Initial Public Offering

On July 30, 2018, we completed our initial public offering ("IPO"), in which we issued and sold 12,535,000 shares of common stock at a price to the public of $23.00 per share, including 1,635,000 shares of common stock purchased by our underwriters from the full exercise of their over-allotment option. All of the shares sold in the IPO were sold by the Company. We received net proceeds of $264.6 million after deducting underwriting discounts and commissions and other offering expenses.

Upon the completion of our IPO, all 15,847,500 shares of our Series A Redeemable Convertible Preferred Stock ("Series A") and 39,538,354 shares of our Series B Redeemable Convertible Preferred Stock ("Series B") automatically converted into an aggregate of 55,385,854 shares of our common stock. Our Amended and Restated Certificate of Incorporation adopted in connection with the IPO authorizes a total of 500,000,000 shares of common stock and 10,000,000 shares of preferred stock.

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. These estimates include, but are not limited to, the determination of the estimated economic life of perpetual licenses for revenue recognition, the estimated period of benefit for deferred commissions, useful lives of long-lived assets, the valuation of stock-based compensation, including the estimated underlying fair value of our common stock prior to our IPO, the incremental borrowing rate for operating leases, and the valuation of deferred tax assets. We base these estimates on historical experience and on various other assumptions that we believe to be reasonable. Actual results could differ significantly from these estimates.

Revenue Recognition

We recognize revenue in order to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. To achieve this, we apply the following steps:

•Identify the contract with a customer

•Identify the performance obligations in the contract

•Determine the transaction price

•Allocate the transaction price to the performance obligations in the contract

•Recognize revenue when or as performance obligations are satisfied

We generate revenue from subscription arrangements for software and cloud-based solutions, perpetual licenses, maintenance associated with perpetual licenses, and professional services and other revenue. We begin to recognize revenue when control of our software or services is transferred to the customer, which for sales made through distributors is concurrent with the transfer to the end user.

The following table presents a summary of revenue:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Subscription revenue	$	75,503	$	53,511	$	209,610	$	146,568
Perpetual license and maintenance revenue	13,797		13,864		40,877		40,753
Professional services and other revenue	2,552		2,065		7,050		4,818
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Subscription Revenue

Subscription arrangements generally have annual or multi-year contractual terms for the use of our software or cloud solutions, including ongoing software updates and the ability to identify the latest cybersecurity vulnerabilities. Revenue is recognized ratably over the subscription term given the critical utility provided by the ongoing updates that are released throughout the contract period.

Perpetual License and Maintenance Revenue

Our perpetual licenses are generally sold with one or more years of maintenance, which include ongoing software updates and the ongoing ability to identify the latest cybersecurity vulnerabilities. Given the critical utility provided by the ongoing software updates and updated ability to identify network vulnerabilities included in maintenance, we combine the perpetual license and the maintenance into a single performance obligation. Perpetual license arrangements generally contain a material right related to the customer’s ability to renew maintenance at a price that is less than the initial license fee. We apply a practical alternative to allocating a portion of the transaction price to the material right performance obligation and estimate a hypothetical transaction price which includes fees for expected maintenance renewals based on the estimated economic life of the perpetual license contracts. We allocate the transaction price between the cybersecurity subscription provided in the initial contract and the material right related to expected contract renewals based on the hypothetical transaction price. We recognize the amount allocated to the combined license and maintenance performance obligation over the initial contractual period, which is generally one year. We recognize the amount allocated to the material right over the expected maintenance renewal period, which begins at the end of the initial contractual term and is generally four years. We have estimated the five-year economic life of perpetual license contracts based on historical contract attrition, expected renewal periods, the lifecycle of the our technology and other factors. While we believe that the estimates we have made are reasonable and appropriate, different assumptions and estimates could materially impact our reported financial results.

Professional Services and Other Revenue

Professional services and other revenue is primarily comprised of advisory services and training related to the deployment and optimization of our products. These services do not result in significant customization of our products. Professional services and other revenue is recognized as the services are performed.

Contracts with Multiple Performance Obligations

In cases where our contracts with customers contain multiple performance obligations, the contract transaction price is allocated on a relative standalone selling price basis. We typically determine standalone selling price based on observable selling prices of our products and services.

Variable Consideration

We record revenue from sales at the net sales price, which is the transaction price, including estimates of variable consideration when applicable. Certain of our customers may be entitled to receive credits and in certain circumstances, refunds, if service level commitments are not met. We have not historically experienced significant incidents affecting the ability to meet these service level commitments and any estimated refunds related to these agreements have not been material.

Sales through our channel network of distributors and resellers are generally discounted as compared to the price that we would sell to an end user. Revenue for sales through our channel network is recorded net of any distributor or reseller margin.

Concentrations

We sell and market our products and services through our field sales force that works closely with our channel partners, which includes a network of distributors and resellers, in developing sales opportunities. We use a two-tiered channel model whereby we sell our products and services to our distributors, which in turn sell to resellers, which then sell to end-users. We derived 91%, 88%, 90%, and 87% of revenue through our channel network in the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018, respectively. One of our distributors accounted for 43% of revenue in the three and nine months ended September 30, 2019 and 46% of revenue in the three and nine months ended September 30, 2018. That same distributor accounted for 40% and 46% of accounts receivable at September 30, 2019 and December 31, 2018, respectively.

Contract Balances

We generally bill our customers in advance and accounts receivable are recorded when we have the right to invoice the customer. Contract liabilities consist of deferred revenue and include customer billings and payments received in advance of performance under the contract. In the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018, we recognized revenue of $84.6 million, $62.5 million, $184.3 million and $133.3 million, respectively, that was included in the deferred revenue balance at the beginning of each of the respective periods.

Remaining Performance Obligations

At September 30, 2019, the future estimated revenue related to unsatisfied performance obligations was $333.4 million, with 74% expected to be recognized as revenue over the succeeding twelve months, and the remainder expected to be recognized over the four years thereafter.

Investments

We currently invest in commercial paper, corporate bonds and U.S. treasury and agency obligations. Our investments are classified as available-for-sale and recorded at fair value, with unrealized gains and losses reported in accumulated

other comprehensive income within stockholders’ equity (deficit). We periodically review our investment portfolio to determine whether investments have indicators of possible impairment.

Deferred Commissions

Sales commissions, including related incremental fringe benefit costs, are considered to be incremental costs of obtaining a contract. Sales commissions on initial sales are not commensurate with sales commissions on contract renewals and therefore are recognized over an estimated period of benefit, which ranges between three and four years for subscription arrangements and five years for perpetual license arrangements. We estimate the period of benefit based on the expected contract term including renewal periods, the lifecycle of our technology, and other factors. Sales commissions on contract renewals are capitalized and amortized ratably over the contract term, with the exception of contracts with renewal periods that are one year or less, in which case the incremental costs are expensed as incurred.

The following summarizes the activity of deferred incremental costs of obtaining a contract in the periods presented:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands)	2019			2018			2019			2018
Beginning balance	$	61,866		$	50,805		$	59,434		$	50,176
Capitalization of contract acquisition costs	9,612			7,138			24,846			16,985
Amortization of deferred contract acquisition costs	(6,955		)	(5,059		)	(19,757		)	(14,277		)
Ending balance	$	64,523		$	52,884		$	64,523		$	52,884

Amortization of deferred contract acquisition costs is included in sales and marketing expense in the consolidated statements of operations.

Leases

We early adopted Accounting Standards Codification Topic 842, Leases ("ASC 842"), as of January 1, 2018 using the modified retrospective method. We determine if an arrangement contains a lease and the classification of that lease, if applicable, at inception. We have elected to not recognize a lease liability or right-of-use ("ROU") asset for short-term leases (leases with a term of twelve months or less). For contracts with lease and non-lease components, we have elected to not allocate the contract consideration, and account for the lease and non-lease components as a single lease component. Additionally, we enter into arrangements to use shared office spaces and other facilities, and have determined that these arrangements do not contain leases as we do not have the right to use an identified asset. Operating leases are included in operating lease ROU assets, operating lease liabilities and operating lease liabilities (net of current portion) in our consolidated balance sheets. Finance leases are included in property and equipment, other current liabilities and other liabilities in our consolidated balance sheets.

ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments under the lease. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The implicit rate within our operating leases is generally not determinable and we use our incremental borrowing rate at the lease commencement date to determine the present value of lease payments. The determination of our incremental borrowing rate requires judgment and is estimated for each lease based on the rate we would have to pay for a collateralized loan with the same term and payments as the lease. We consider various factors, including our current borrowing rate, level of collateralization, estimated credit rating and currency of the lease. The operating lease ROU asset also includes any lease prepayments, offset by lease incentives. Certain of our leases include options to extend or terminate the lease. Options to extend or terminate a lease are considered in connection with calculating the ROU asset and related lease liability when it is reasonably certain that we will exercise that option.

Lease expense for lease payments is recognized on a straight-line basis over the term of the lease.

Recent Accounting Pronouncements Not Yet Adopted

In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-13 — Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This ASU amends guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities to require that credit losses on available-for-sale debt securities be presented as an allowance rather than as a write-down. The measurement of credit losses for newly recognized financial assets and subsequent changes in the allowance for credit losses are recorded in the statements of operations. This guidance is effective for us beginning January 1, 2020, and will be adopted using the modified-retrospective method. We are currently evaluating the potential impact of this standard on our consolidated financial statements.

In August 2018, the FASB issued ASU No. 2018-15 — Intangibles — Goodwill and Other — Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. Under this ASU, implementation costs related to a cloud computing arrangement that is a service contract will be capitalized consistent with the requirements for capitalizing internal-use software development costs. The capitalized implementation costs are subsequently expensed over the term of the hosting arrangement. This guidance is effective for us beginning January 1, 2020, and will be adopted on a prospective basis. We are currently evaluating the potential impact of this standard.

Cash and Cash Equivalents and Short-Term Investments

9 Months Ended

Sep. 30, 2019

Cash and Cash Equivalents [Abstract]

Cash and Cash Equivalents and Short-Term Investments

At September 30, 2019 and December 31, 2018, cash and cash equivalents excluded $0.3 million of restricted cash, which is related to an account established as collateral for a lease arrangement and was included in other assets on the consolidated balance sheets.

The following tables summarize the amortized cost, unrealized gain and loss and estimated fair value of cash equivalents and short-term investments:



	September 30, 2019
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Cash equivalents:
Money market funds	$	28,043	$	—	$	—		$	28,043
Commercial paper	4,496		—		—			4,496
Total cash equivalents	$	32,539	$	—	$	—		$	32,539

Short-term investments:
Commercial paper	$	56,754	$	—	$	—		$	56,754
Corporate bonds	15,993		32		—			16,025
U.S. Treasury and agency obligations	52,526		35		(7		)	52,554
Total short-term investments	$	125,273	$	67	$	(7	)	$	125,333



	December 31, 2018
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Cash equivalents:
Money market funds	$	38,022	$	—	$	—	$	38,022
Total cash equivalents	$	38,022	$	—	$	—	$	38,022

Short-term investments:
Commercial paper	$	79,634	$	—	$	—	$	79,634
Corporate bonds	16,119		—		—		16,119
U.S. Treasury and agency obligations	22,366		—		—		22,366
Total short-term investments	$	118,119	$	—	$	—	$	118,119

For any investments that were in an unrealized loss position, we considered if we intended on selling the investments before maturity and if it is more-likely-than-not that we would have to sell the security before the recovery of the amortized cost basis. We concluded that there were no other-than-temporary impairments at September 30, 2019.

At September 30, 2019 and December 31, 2018, all of our short-term investments had maturities within the next twelve months.

Fair Value Measurements

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

We measure certain financial instruments at fair value using a fair value hierarchy. In the hierarchy, assets are classified based on the lowest level inputs used in valuation into the following categories:


•	Level 1 — Quoted prices in active markets for identical assets and liabilities;


•	Level 2 — Observable inputs including quoted market prices for similar assets and liabilities in active markets, quoted prices for identical assets and liabilities in inactive markets, or inputs that are corroborated by observable market data; and


•	Level 3 — Unobservable inputs.

The following tables summarize assets that are measured at fair value on a recurring basis:



	September 30, 2019
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	28,043	$	—	$	—	$	28,043
Commercial paper	—		4,496		—		4,496
	$	28,043	$	4,496	$	—	$	32,539

Short-term investments
Commercial paper	$	—	$	56,754	$	—	$	56,754
Corporate bonds	—		16,025		—		16,025
U.S. Treasury and agency obligations	—		52,554		—		52,554
	$	—	$	125,333	$	—	$	125,333



	December 31, 2018
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	38,022	$	—	$	—	$	38,022
	$	38,022	$	—	$	—	$	38,022

Short-term investments
Commercial paper	$	—	$	79,634	$	—	$	79,634
Corporate bonds	—		16,119		—		16,119
U.S. Treasury and agency obligations	—		22,366		—		22,366
	$	—	$	118,119	$	—	$	118,119

We did not have any liabilities measured and recorded at fair value at September 30, 2019 or December 31, 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment, Net

9 Months Ended

Sep. 30, 2019

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

Property and equipment, net consisted of the following:



(in thousands)	September 30, 2019			December 31, 2018
Computer software and equipment	$	20,221		$	13,038
Furniture and fixtures	3,738			2,376
Leasehold improvements	9,230			7,266
Right-of-use assets under finance leases	1,866			1,854
Total	35,055			24,534
Less: accumulated depreciation and amortization	(16,530		)	(13,186		)
Property and equipment, net	$	18,525		$	11,348

Depreciation and amortization related to property and equipment was $1.4 million, $1.4 million, $4.2 million and $4.1 million in the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018, respectively.

Leases

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Leases

We have operating leases for office facilities and finance leases for computer and office equipment. Our leases have remaining terms of less than one year to just over twelve years, some of which include one or more options to renew, with renewal terms up to five years and some of which include options to terminate the leases within the next three to six years. The ROU assets and liabilities at September 30, 2019 assume the option to early terminate one of our leases in 2021 and one of our leases in 2025.

During the three months ended September 30, 2019 we took possession of the leased office space for our future headquarters in Columbia, Maryland. We recorded an initial ROU asset of $32.3 million and a lease liability of $32.0 million, with a lease term of 147 months. Future lease payments related to this lease are $67.7 million and the lease payments are expected to commence in the first quarter of 2021.

The components of lease expense were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Operating lease cost	$	1,763	$	960	$	3,844	$	2,730

Finance lease cost
Amortization of ROU assets	$	157	$	155	$	465	$	459
Interest on lease liabilities	2		10		5		29
Total finance lease cost	$	159	$	165	$	470	$	488

Rent expense for short-term leases in the three and nine months ended September 30, 2019 and 2018 was not material.

Supplemental information related to leases was as follows:



	September 30, 2019	December 31, 2018
Operating leases
Weighted average remaining lease term	10.2 years	3.1 years
Weighted average discount rate	5.9%	7.1%



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
ROU assets obtained in exchange for lease obligations
Operating leases	$	32,292	$	263	$	34,490	$	1,525
Finance leases	—		4		11		4

Maturities of operating lease liabilities at September 30, 2019 were as follows:



(in thousands)
Year ending December 31,
2019⁽¹⁾	$	994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589		)
Less: Tenant incentives	(14,013		)
Total	$	41,758

_______________

(1) Represents the three months ending December 31, 2019.

Leases

The components of lease expense were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Operating lease cost	$	1,763	$	960	$	3,844	$	2,730

Finance lease cost
Amortization of ROU assets	$	157	$	155	$	465	$	459
Interest on lease liabilities	2		10		5		29
Total finance lease cost	$	159	$	165	$	470	$	488

Rent expense for short-term leases in the three and nine months ended September 30, 2019 and 2018 was not material.

Supplemental information related to leases was as follows:



	September 30, 2019	December 31, 2018
Operating leases
Weighted average remaining lease term	10.2 years	3.1 years
Weighted average discount rate	5.9%	7.1%



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
ROU assets obtained in exchange for lease obligations
Operating leases	$	32,292	$	263	$	34,490	$	1,525
Finance leases	—		4		11		4

Maturities of operating lease liabilities at September 30, 2019 were as follows:



(in thousands)
Year ending December 31,
2019⁽¹⁾	$	994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589		)
Less: Tenant incentives	(14,013		)
Total	$	41,758

_______________

(1) Represents the three months ending December 31, 2019.

Debt	9 Months Ended
Debt	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	Debt On May 4, 2017, we entered into a $25.0 million revolving credit facility (“Credit Facility”) with Silicon Valley Bank, which is available for use until May 4, 2020. There were no borrowings under the Credit Facility during the nine months ended September 30, 2019 or in 2018.

Redeemable Convertible Preferred Stock and Common Stock	9 Months Ended
Redeemable Convertible Preferred Stock and Common Stock	Sep. 30, 2019
Stockholders' Equity Note [Abstract]
Redeemable Convertible Preferred Stock and Common Stock	Redeemable Convertible Preferred Stock and Common Stock Redeemable Convertible Preferred Stock In October 2012, Tenable, Inc. (now a wholly owned subsidiary of Tenable Holdings, Inc.) issued 15,847,500 shares of Series A redeemable convertible preferred stock. In December 2015, we issued 15,847,500 shares, par value of $0.01, of Series A redeemable convertible preferred stock ("Series A") in exchange for Series A redeemable convertible preferred stock of Tenable, Inc. in connection with a recapitalization. This exchange was made on a one for one basis. In addition, we authorized 42,000,000 shares and issued 39,538,354 shares, par value of $0.01, of Series B redeemable convertible preferred stock ("Series B"). Upon completion of our IPO, Series A and Series B (together, the “Redeemable Convertible Preferred Stock”) automatically converted into an aggregate of 55,385,854 shares of our common stock. We accreted the Redeemable Convertible Preferred Stock to the redemption price at the redemption date using the effective interest method. Upon completion of our IPO, the accretion rights of the Redeemable Convertible Preferred Stock were terminated. Upon the completion of our IPO, we filed an Amended and Restated Certificate of Incorporation, authorizing a total of 500,000,000 shares of common stock and 10,000,000 shares of preferred stock. There were no shares of preferred stock issued or outstanding at September 30, 2019 or December 31, 2018. Common Stock The voting, dividend, and liquidation rights of common stockholders are subject to, and qualified by, the rights of preferred stockholders. The common stockholders are entitled to receive dividends when, as and if, declared by the Board of Directors, subject to preferential dividend rights of preferred stockholders. Upon dissolution or liquidation, our common stockholders will be entitled to receive all assets available for distribution to stockholders, subject to any preferential rights of preferred stockholders.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

In 2018, our Board of Directors adopted, and our stockholders approved, our 2018 Equity Incentive Plan ("2018 Plan"), which became effective upon the execution of the underwriting agreement related to our IPO, and no further grants were made under our 2016 Stock Incentive Plan ("2016 Plan"). Any shares subject to stock options or other stock awards granted under our 2016 Plan, 2012 Stock Incentive Plan or 2002 Stock Incentive Plan that would have otherwise returned to such plan (such as upon the expiration or termination of a stock award prior to vesting) were added to, and are available for issuance under, our 2018 Plan. In addition, the number of shares of our common stock reserved for issuance under our 2018 Plan automatically increases on January 1 of each year, beginning on January 1, 2019 and continuing through and including January 1, 2028, by 5% of the total number of shares of our capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by our Board of Directors. At September 30, 2019, there were 15,052,780 shares available for grant under the 2018 Plan.

Stock options granted under our stock incentive plans have a maximum term of ten years, generally vest over a period of three to four years, and the exercise price cannot be less than the fair market value on the date of grant. Restricted stock units ("RSUs") granted under our stock incentive plans generally vest over a period of two to four years.

Stock-based compensation expense included in the consolidated statements of operations was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Cost of revenue	$	694	$	692	$	2,088	$	883
Sales and marketing	3,521		2,707		11,102		3,984
Research and development	2,124		2,427		6,595		3,594
General and administrative	4,160		2,957		11,406		5,745
Total stock-based compensation expense	$	10,499	$	8,783	$	31,191	$	14,206

At September 30, 2019, the total unrecognized stock-based compensation expense related to outstanding stock options was $29.8 million, which is expected to be recognized over an estimated remaining weighted average period of 2.4 years.

At September 30, 2019, the unrecognized stock-based compensation expense related to unvested awards of restricted stock was $2.1 million, which is expected to be recognized over an estimated remaining period of 1.3 years.

At September 30, 2019, the unrecognized stock-based compensation expense related to unvested restricted stock units was $62.4 million, which is expected to be recognized over an estimated remaining weighted average period of 3.2 years.

Stock Options

A summary of our stock option activity is presented below:



(in thousands, except for per share data and years)	Number of Shares	Weighted Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2018	19,219	$	7.78	8.0	$	277,114
Granted	—	—
Exercised	(3,625)	4.26
Forfeited/canceled	(1,652)	10.03
Outstanding at September 30, 2019	13,942	8.43		7.5	194,654
Exercisable at September 30, 2019	6,470	5.80		6.7	107,297

At September 30, 2019, there were 13.9 million stock options that were vested and expected to vest.

Restricted Stock and Restricted Stock Units

A summary of our restricted stock and restricted stock units activity is presented below:



	Restricted Stock				Restricted Stock Units
(in thousands, except for per share data)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value
Unvested balance at December 31, 2018	890		$	4.25	1,129		$	18.90
Granted	—		—		2,454		28.10
Vested	(296	)	4.25		(432	)	17.20
Forfeited	—		—		(291	)	23.96
Unvested balance at September 30, 2019	594		4.25		2,860		26.54

The grant date fair value was based on the estimated fair value of our common stock on the date of grant. RSUs granted before July 30, 2018 vest upon the satisfaction of both service-based and performance-based vesting conditions. The performance-based condition was satisfied upon the completion of our IPO. RSUs granted after July 30, 2018 vest upon the satisfaction of a service-based vesting condition.

Compensation expense for restricted stock and RSUs is recognized on a straight-line basis over the requisite service period, with the exception of RSUs that include performance-based vesting conditions, which are expensed using the accelerated attribution method.

2018 Employee Stock Purchase Plan

In 2018, our Board of Directors adopted, and our stockholders approved, our 2018 Employee Stock Purchase Plan ("2018 ESPP"). Our 2018 ESPP became effective upon the execution of the underwriting agreement related to our IPO. The number of shares of our common stock reserved for issuance under our 2018 ESPP automatically increases on January 1 of each year, beginning on January 1, 2019 and continuing through and including January 1, 2028, by the lesser of (1) 1.5% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year, (2) 8,000,000 shares of our common stock or (3) such lesser number of shares of common stock as determined by our Board of Directors. At September 30, 2019, there were 4,620,087 shares reserved for issuance under the 2018 ESPP.

Under our 2018 ESPP, employees may set aside up to 15% of their gross earnings, on an after-tax basis, to purchase our common stock at a discounted price, which is calculated at 85% of the lower of the fair market value of our common stock on the first day of an offering or on the date of purchase. The 2018 ESPP permits offerings up to 27 months in duration, with one or more purchase periods in each offering. Additionally, in cases where the fair market value of a share of our common stock on the first day of a new purchase period within an offering is less than or equal to the fair market value of a share of our common stock at the beginning of the offering, that offering will be terminated and participants will be automatically enrolled in a new offering with a new 24 month duration, with purchase periods every six months.

In the nine months ended September 30, 2019, employees purchased 776,809 shares of our common stock at a weighted average price of $19.48 per share, resulting in cash proceeds to us of $15.1 million.

At September 30, 2019, there was $1.5 million of employee contributions to the 2018 ESPP included in accrued compensation. The unrecognized stock-based compensation expense related to our 2018 ESPP was $11.3 million, which is expected to be recognized over the remaining offering period of 1.9 years.

The fair value of the 2018 ESPP purchase rights was estimated on the grant date using a Black-Scholes option-pricing model and the following assumptions:



Expected term (in years)	0.5 — 2.1
Expected volatility	31.9% — 44.6%
Risk-free interest rate	1.5% — 2.7%
Expected dividend yield	—

Net Loss Per Share Attributable to Common Stockholders

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except per share data)	2019			2018			2019			2018
Net loss attributable to common stockholders	$	(17,640	)	$	(20,924	)	$	(60,708	)	$	(54,341	)

Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted	96,709			74,261			95,433			40,688
Net loss per share attributable to common stockholders, basic and diluted	$	(0.18	)	$	(0.28	)	$	(0.64	)	$	(1.34	)

The following potentially dilutive securities have been excluded from the diluted per share calculations because they would have been antidilutive:



	Three and Nine Months Ended September 30,
(in thousands)	2019	2018
Stock options	13,942	19,387
Restricted stock units	2,860	1,050
Restricted shares	594	989
Shares to be issued under the 2018 ESPP	64	118
Total	17,460	21,544

Geographic Information

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Geographic Information

We operate as one operating segment. Our Chief Executive Officer, who is our chief operating decision maker, reviews financial information on a consolidated basis for purposes of making operating decisions, allocating resources, and evaluating financial performance.

Revenue by region, based on the address of the end user as specified in our subscription, license or service agreements, was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Americas	$	62,413	$	49,391	$	177,392	$	137,868
Europe, Middle East and Africa	19,968		14,002		56,123		38,218
Asia Pacific	9,471		6,047		24,022		16,053
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Customers located in the United States accounted for 63%, 66%, 64%, and 67% of revenue in the three months ended September 30, 2019 and 2018 and the nine months ended September 30, 2019 and 2018, respectively. No other country accounted for 10% or more of revenue in the periods presented.

Our property and equipment, net by geographic area is summarized as follows:



(in thousands)	September 30, 2019		December 31, 2018
United States	$	13,612	$	6,487
International	4,913		4,861
Property and equipment, net	$	18,525	$	11,348

Business and Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

•Identify the contract with a customer

•Identify the performance obligations in the contract

•Determine the transaction price

•Allocate the transaction price to the performance obligations in the contract

•Recognize revenue when or as performance obligations are satisfied

The following table presents a summary of revenue:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Subscription revenue	$	75,503	$	53,511	$	209,610	$	146,568
Perpetual license and maintenance revenue	13,797		13,864		40,877		40,753
Professional services and other revenue	2,552		2,065		7,050		4,818
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Subscription Revenue

Perpetual License and Maintenance Revenue

Professional Services and Other Revenue

Contracts with Multiple Performance Obligations

Variable Consideration

Concentrations

Contract Balances

We generally bill our customers in advance and accounts receivable are recorded when we have the right to invoice the customer.

Investments

other comprehensive income within stockholders’ equity (deficit). We periodically review our investment portfolio to determine whether investments have indicators of possible impairment.

Leases

Lease expense for lease payments is recognized on a straight-line basis over the term of the lease.

Recent Accounting Pronouncements Not Yet Adopted

Business and Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of revenue

The following table presents a summary of revenue:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Subscription revenue	$	75,503	$	53,511	$	209,610	$	146,568
Perpetual license and maintenance revenue	13,797		13,864		40,877		40,753
Professional services and other revenue	2,552		2,065		7,050		4,818
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Activity of deferred contract costs

The following summarizes the activity of deferred incremental costs of obtaining a contract in the periods presented:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands)	2019			2018			2019			2018
Beginning balance	$	61,866		$	50,805		$	59,434		$	50,176
Capitalization of contract acquisition costs	9,612			7,138			24,846			16,985
Amortization of deferred contract acquisition costs	(6,955		)	(5,059		)	(19,757		)	(14,277		)
Ending balance	$	64,523		$	52,884		$	64,523		$	52,884

Cash and Cash Equivalents and Short-Term Investments (Tables)

9 Months Ended

Sep. 30, 2019

Cash and Cash Equivalents [Abstract]

Summary of amortized cost, unrealized gain and loss and estimated fair value

The following tables summarize the amortized cost, unrealized gain and loss and estimated fair value of cash equivalents and short-term investments:



	September 30, 2019
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Cash equivalents:
Money market funds	$	28,043	$	—	$	—		$	28,043
Commercial paper	4,496		—		—			4,496
Total cash equivalents	$	32,539	$	—	$	—		$	32,539

Short-term investments:
Commercial paper	$	56,754	$	—	$	—		$	56,754
Corporate bonds	15,993		32		—			16,025
U.S. Treasury and agency obligations	52,526		35		(7		)	52,554
Total short-term investments	$	125,273	$	67	$	(7	)	$	125,333



	December 31, 2018
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Cash equivalents:
Money market funds	$	38,022	$	—	$	—	$	38,022
Total cash equivalents	$	38,022	$	—	$	—	$	38,022

Short-term investments:
Commercial paper	$	79,634	$	—	$	—	$	79,634
Corporate bonds	16,119		—		—		16,119
U.S. Treasury and agency obligations	22,366		—		—		22,366
Total short-term investments	$	118,119	$	—	$	—	$	118,119

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Schedule of assets measured at fair value on recurring basis

The following tables summarize assets that are measured at fair value on a recurring basis:



	September 30, 2019
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	28,043	$	—	$	—	$	28,043
Commercial paper	—		4,496		—		4,496
	$	28,043	$	4,496	$	—	$	32,539

Short-term investments
Commercial paper	$	—	$	56,754	$	—	$	56,754
Corporate bonds	—		16,025		—		16,025
U.S. Treasury and agency obligations	—		52,554		—		52,554
	$	—	$	125,333	$	—	$	125,333



	December 31, 2018
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	38,022	$	—	$	—	$	38,022
	$	38,022	$	—	$	—	$	38,022

Short-term investments
Commercial paper	$	—	$	79,634	$	—	$	79,634
Corporate bonds	—		16,119		—		16,119
U.S. Treasury and agency obligations	—		22,366		—		22,366
	$	—	$	118,119	$	—	$	118,119

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Property and Equipment, Net (Tables)

9 Months Ended

Sep. 30, 2019

Property, Plant and Equipment [Abstract]

Property and equipment, net

Property and equipment, net consisted of the following:



(in thousands)	September 30, 2019			December 31, 2018
Computer software and equipment	$	20,221		$	13,038
Furniture and fixtures	3,738			2,376
Leasehold improvements	9,230			7,266
Right-of-use assets under finance leases	1,866			1,854
Total	35,055			24,534
Less: accumulated depreciation and amortization	(16,530		)	(13,186		)
Property and equipment, net	$	18,525		$	11,348

Leases (Tables)

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Components of leases

Supplemental information related to leases was as follows:



	September 30, 2019	December 31, 2018
Operating leases
Weighted average remaining lease term	10.2 years	3.1 years
Weighted average discount rate	5.9%	7.1%



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
ROU assets obtained in exchange for lease obligations
Operating leases	$	32,292	$	263	$	34,490	$	1,525
Finance leases	—		4		11		4

The components of lease expense were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Operating lease cost	$	1,763	$	960	$	3,844	$	2,730

Finance lease cost
Amortization of ROU assets	$	157	$	155	$	465	$	459
Interest on lease liabilities	2		10		5		29
Total finance lease cost	$	159	$	165	$	470	$	488

Schedule of maturities of operating lease liabilities

Maturities of operating lease liabilities at September 30, 2019 were as follows:



(in thousands)
Year ending December 31,
2019⁽¹⁾	$	994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589		)
Less: Tenant incentives	(14,013		)
Total	$	41,758

_______________

(1) Represents the three months ending December 31, 2019.

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Stock-based compensation expense

Stock-based compensation expense included in the consolidated statements of operations was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Cost of revenue	$	694	$	692	$	2,088	$	883
Sales and marketing	3,521		2,707		11,102		3,984
Research and development	2,124		2,427		6,595		3,594
General and administrative	4,160		2,957		11,406		5,745
Total stock-based compensation expense	$	10,499	$	8,783	$	31,191	$	14,206

Stock option activity

A summary of our stock option activity is presented below:



(in thousands, except for per share data and years)	Number of Shares	Weighted Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2018	19,219	$	7.78	8.0	$	277,114
Granted	—	—
Exercised	(3,625)	4.26
Forfeited/canceled	(1,652)	10.03
Outstanding at September 30, 2019	13,942	8.43		7.5	194,654
Exercisable at September 30, 2019	6,470	5.80		6.7	107,297

Summary of restricted stock and restricted stock units

A summary of our restricted stock and restricted stock units activity is presented below:



	Restricted Stock				Restricted Stock Units
(in thousands, except for per share data)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value
Unvested balance at December 31, 2018	890		$	4.25	1,129		$	18.90
Granted	—		—		2,454		28.10
Vested	(296	)	4.25		(432	)	17.20
Forfeited	—		—		(291	)	23.96
Unvested balance at September 30, 2019	594		4.25		2,860		26.54

ESPP valuation assumptions

The fair value of the 2018 ESPP purchase rights was estimated on the grant date using a Black-Scholes option-pricing model and the following assumptions:



Expected term (in years)	0.5 — 2.1
Expected volatility	31.9% — 44.6%
Risk-free interest rate	1.5% — 2.7%
Expected dividend yield	—

Net Loss Per Share Attributable to Common Stockholders (Tables)

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Computation of basic and diluted net loss per share

The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except per share data)	2019			2018			2019			2018
Net loss attributable to common stockholders	$	(17,640	)	$	(20,924	)	$	(60,708	)	$	(54,341	)

Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted	96,709			74,261			95,433			40,688
Net loss per share attributable to common stockholders, basic and diluted	$	(0.18	)	$	(0.28	)	$	(0.64	)	$	(1.34	)

Potentially dilutive securities

The following potentially dilutive securities have been excluded from the diluted per share calculations because they would have been antidilutive:



	Three and Nine Months Ended September 30,
(in thousands)	2019	2018
Stock options	13,942	19,387
Restricted stock units	2,860	1,050
Restricted shares	594	989
Shares to be issued under the 2018 ESPP	64	118
Total	17,460	21,544

Geographic Information (Tables)

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Revenue by region

Revenue by region, based on the address of the end user as specified in our subscription, license or service agreements, was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Americas	$	62,413	$	49,391	$	177,392	$	137,868
Europe, Middle East and Africa	19,968		14,002		56,123		38,218
Asia Pacific	9,471		6,047		24,022		16,053
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Property and equipment, net by geographic area

Our property and equipment, net by geographic area is summarized as follows:



(in thousands)	September 30, 2019		December 31, 2018
United States	$	13,612	$	6,487
International	4,913		4,861
Property and equipment, net	$	18,525	$	11,348

Business and Summary of Significant Accounting Policies - Initial Public Offering (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended	9 Months Ended
	Jul. 30, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, authorized (in shares)	500,000,000			500,000,000	500,000,000
Preferred stock, authorized (in shares)	10,000,000
IPO
Class of Stock [Line Items]
Stock sold, price per share (in usd per share)	$ 23.00
Net proceeds from sale of stock	$ 264.6
Common Stock
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)		55,386,000	55,386,000
Common Stock \| IPO
Class of Stock [Line Items]
Stock sold (in shares)	12,535,000
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	55,385,854
Common Stock \| Over-allotment option
Class of Stock [Line Items]
Stock sold (in shares)	1,635,000
Redeemable convertible Series A preferred stock \| IPO
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	15,847,500
Redeemable convertible Series B preferred stock \| IPO
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	39,538,354

Business and Summary of Significant Accounting Policies - Summary of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 91,852	$ 69,440	$ 257,537	$ 192,139
Subscription revenue
Disaggregation of Revenue [Line Items]
Revenue	75,503	53,511	209,610	146,568
Perpetual license and maintenance revenue
Disaggregation of Revenue [Line Items]
Revenue	13,797	13,864	40,877	40,753
Professional services and other revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 2,552	$ 2,065	$ 7,050	$ 4,818

Business and Summary of Significant Accounting Policies - Perpetual License and Maintenance Revenue (Details) - Perpetual license and maintenance revenue	9 Months Ended
	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
License and maintenance period	1 year
Estimated maintenance renewal period	4 years
Economic life of perpetual license contracts	5 years

Business and Summary of Significant Accounting Policies - Concentrations (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
One distributor \| Revenue \| Customer concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage	43.00%	46.00%	43.00%	46.00%
One distributor \| Accounts receivable \| Customer concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage			40.00%		46.00%
Channel network \| Revenue \| Sales method risk
Concentration Risk [Line Items]
Concentration risk, percentage	91.00%	88.00%	90.00%	87.00%

Business and Summary of Significant Accounting Policies - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue recognized that was included in deferred revenue	$ 84.6	$ 62.5	$ 184.3	$ 133.3

Business and Summary of Significant Accounting Policies - Remaining Performance Obligations (Details) $ in Millions	Sep. 30, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Future estimated revenue	$ 333.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected recognized percentage over succeeding 12 months	74.00%
Expected timing of satisfaction	4 years

Business and Summary of Significant Accounting Policies - Deferred Commissions (Details)	Sep. 30, 2019
Perpetual license and maintenance revenue
Capitalized Contract Cost [Line Items]
Estimated period of benefit	5 years
Minimum \| Subscription revenue
Capitalized Contract Cost [Line Items]
Estimated period of benefit	3 years
Maximum \| Subscription revenue
Capitalized Contract Cost [Line Items]
Estimated period of benefit	4 years

Business and Summary of Significant Accounting Policies - Activity of Deferred Contract Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Capitalized Contract Cost [Roll Forward]
Beginning balance	$ 61,866	$ 50,805	$ 59,434	$ 50,176
Capitalization of contract acquisition costs	9,612	7,138	24,846	16,985
Amortization of deferred contract acquisition costs	(6,955)	(5,059)	(19,757)	(14,277)
Ending balance	$ 64,523	$ 52,884	$ 64,523	$ 52,884

Cash and Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Restricted cash	$ 300	$ 300
Cash and Cash Equivalents [Line Items]
Amortized Cost	125,273	118,119
Unrealized Gain	67	0
Unrealized Loss	(7)	0
Estimated fair value	125,333	118,119
Commercial paper
Cash and Cash Equivalents [Line Items]
Amortized Cost	56,754	79,634
Unrealized Gain	0	0
Unrealized Loss	0	0
Estimated fair value	56,754	79,634
Corporate bonds
Cash and Cash Equivalents [Line Items]
Amortized Cost	15,993	16,119
Unrealized Gain	32	0
Unrealized Loss	0	0
Estimated fair value	16,025	16,119
U.S. Treasury and agency obligations
Cash and Cash Equivalents [Line Items]
Amortized Cost	52,526	22,366
Unrealized Gain	35	0
Unrealized Loss	(7)	0
Estimated fair value	52,554	22,366
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	28,043	38,022
Commercial paper
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	4,496
Cash equivalents
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 32,539	$ 38,022

Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total	$ 35,055		$ 35,055		$ 24,534
Less: accumulated depreciation and amortization	(16,530)		(16,530)		(13,186)
Property and equipment, net	18,525		18,525		11,348
Depreciation and amortization	1,400	$ 1,400	4,200	$ 4,100
Computer software and equipment
Property, Plant and Equipment [Line Items]
Total	20,221		20,221		13,038
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	3,738		3,738		2,376
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total	9,230		9,230		7,266
Right-of-use assets under finance leases
Property, Plant and Equipment [Line Items]
Total	$ 1,866		$ 1,866		$ 1,854

Leases - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
Leases - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Renewal term	5 years
Operating lease right-of-use assets	$ 40,346	$ 8,504
Lease liability	41,758
Lease payments expected to commence	$ 78,360
Minimum
Lessee, Lease, Description [Line Items]
Remaining term of leases	1 year
Options to terminate lease	3 years
Maximum
Lessee, Lease, Description [Line Items]
Remaining term of leases	12 years
Options to terminate lease	6 years
Columbia, Maryland
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 32,300
Lease liability	$ 32,000
Initial term of contract	147 months
Lease payments expected to commence	$ 67,700

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating lease cost	$ 1,763	$ 960	$ 3,844	$ 2,730
Amortization of ROU assets	157	155	465	459
Interest on lease liabilities	2	10	5	29
Total finance lease cost	$ 159	$ 165	$ 470	$ 488

Leases - Supplemental Information Related to Leases (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating leases
Weighted average remaining lease term	10 years 2 months 12 days		10 years 2 months 12 days		3 years 1 month 6 days
Weighted average discount rate	5.90%		5.90%		7.10%
ROU assets obtained in exchange for lease obligations
Operating leases	$ 32,292	$ 263	$ 34,490	$ 1,525
Finance leases	$ 0	$ 4	$ 11	$ 4

Leases - Operating Lease Liability Maturities (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Leases [Abstract]
2019	$ 994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589)
Less: Tenant incentives	(14,013)
Total	$ 41,758

Debt (Details) - USD ($)	9 Months Ended	12 Months Ended
Debt (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018	May 04, 2017
Line of Credit Facility [Line Items]
Borrowings outstanding		$ 0
Silicon Valley Bank
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity			$ 25,000,000.0
Borrowings outstanding	$ 0

Redeemable Convertible Preferred Stock and Common Stock (Details)		1 Months Ended		3 Months Ended	9 Months Ended
	Jul. 30, 2018 shares	Dec. 31, 2015 $ / shares shares	Oct. 31, 2012 shares	Sep. 30, 2018 shares	Sep. 30, 2018 shares	Sep. 30, 2019 shares	Dec. 31, 2018 shares
Class of Stock [Line Items]
Conversion ratio		1
Common stock, authorized (in shares)	500,000,000					500,000,000	500,000,000
Preferred stock, authorized (in shares)	10,000,000
Preferred stock, shares issued and outstanding (in shares)						0	0
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Stock sold (in shares)		15,847,500	15,847,500
Redeemable convertible preferred stock, par value (in usd per share) \| $ / shares		$ 0.01
Series B Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Stock sold (in shares)		39,538,354
Redeemable convertible preferred stock, par value (in usd per share) \| $ / shares		$ 0.01
Redeemable convertible preferred stock, shares authorized (in shares)		42,000,000
Common Stock
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)				55,386,000	55,386,000
Common Stock \| IPO
Class of Stock [Line Items]
Stock sold (in shares)	12,535,000
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	55,385,854

Stock-Based Compensation - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense, outstanding stock options	$ 29.8
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares reserved for issuance	5.00%
Shares available for grant (in shares) \| shares	15,052,780
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, stock incentive plans, maximum term	10 years
Estimated remaining weighted average period	2 years 4 months 24 days
Stock options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	3 years
Stock options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	4 years
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated remaining weighted average period	1 year 3 months 18 days
Unrecognized stock-based compensation expense, unvested restricted stock or RSUs	$ 2.1
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated remaining weighted average period	3 years 2 months 12 days
Unrecognized stock-based compensation expense, unvested restricted stock or RSUs	$ 62.4
Restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	2 years
Restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	4 years

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 10,499	$ 8,783	$ 31,191	$ 14,206
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	694	692	2,088	883
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	3,521	2,707	11,102	3,984
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	2,124	2,427	6,595	3,594
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 4,160	$ 2,957	$ 11,406	$ 5,745

Stock-Based Compensation - Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Number of Shares
Number of shares outstanding, beginning of period (in shares) \| shares	19,219
Number of shares, granted (in shares) \| shares	0
Number of shares, exercised (in shares) \| shares	(3,625)
Number of shares, forfeited/canceled (in shares) \| shares	(1,652)
Number of shares outstanding, end of period (in shares) \| shares	13,942	19,219
Number of shares exercisable (in shares) \| shares	6,470
Weighted Average Exercise Price
Weighted average exercise price, outstanding, beginning of period (in USD per share) \| $ / shares	$ 7.78
Weighted average exercise price, granted (in USD per share) \| $ / shares	0
Weighted average exercise price, exercised (in USD per share) \| $ / shares	4.26
Weighted average exercise price, forfeited/canceled (in USD per share) \| $ / shares	10.03
Weighted average exercise price, outstanding, end of period (in USD per share) \| $ / shares	8.43	$ 7.78
Weighted average exercise price, exercisable (in USD per share) \| $ / shares	$ 5.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term (in years), outstanding	7 years 6 months	8 years
Weighted average remaining contractual term (in years), exercisable	6 years 8 months 12 days
Aggregate intrinsic value, outstanding \| $	$ 194,654	$ 277,114
Aggregate intrinsic value, exercisable \| $	$ 107,297

Stock-Based Compensation - Stock Option Activity (Narrative) (Details) shares in Millions	Sep. 30, 2019 shares
Share-based Payment Arrangement [Abstract]
Stock options vested and expected to vest (in shares)	13.9

Stock-Based Compensation - Restricted Stock and Restricted Stock Units (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2019 $ / shares shares
Restricted shares
Number of Shares
Number of shares unvested, beginning of period (in shares) \| shares	890
Number of shares, granted (in shares) \| shares	0
Number of shares, vested (in shares) \| shares	(296)
Number of shares, forfeited (in shares) \| shares	0
Number of shares unvested, end of period (in shares) \| shares	594
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning of period (in USD per share) \| $ / shares	$ 4.25
Weighted average grant date fair value, granted (in USD per share) \| $ / shares	0
Weighted average grant date fair value, vested (in USD per share) \| $ / shares	4.25
Weighted average grant date fair value, forfeited (in USD per share) \| $ / shares	0
Weighted average grant date fair value, end of period (in USD per share) \| $ / shares	$ 4.25
Restricted stock units
Number of Shares
Number of shares unvested, beginning of period (in shares) \| shares	1,129
Number of shares, granted (in shares) \| shares	2,454
Number of shares, vested (in shares) \| shares	(432)
Number of shares, forfeited (in shares) \| shares	(291)
Number of shares unvested, end of period (in shares) \| shares	2,860
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning of period (in USD per share) \| $ / shares	$ 18.90
Weighted average grant date fair value, granted (in USD per share) \| $ / shares	28.10
Weighted average grant date fair value, vested (in USD per share) \| $ / shares	17.20
Weighted average grant date fair value, forfeited (in USD per share) \| $ / shares	23.96
Weighted average grant date fair value, end of period (in USD per share) \| $ / shares	$ 26.54

Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from stock issued in connection with the employee stock purchase plan	$ 15,129	$ 0
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares reserved for issuance	1.50%
Common stock, annual increase (in shares)	8,000,000
Common stock reserved for issuance (in shares)	4,620,087
Percentage of employee earnings allowed	15.00%
Discount price percentage	85.00%
Offering period (up to)	27 months
Common stock purchased (in shares)	776,809
Share price (in USD per share)	$ 19.48
Employee contributions	$ 1,500
Unrecognized stock-based compensation expense	$ 11,300
Remaining offering period	1 year 10 months 24 days

Stock-Based Compensation - Fair Value Assumptions (Details) - Employee stock purchase plan	9 Months Ended
	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	31.90%
Expected volatility, maximum	44.60%
Risk - free interest rate, minimum	1.50%
Risk - free interest rate, maximum	2.70%
Expected dividend yield	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	2 years 1 month 6 days

Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net loss attributable to common stockholders	$ (17,640)	$ (20,924)	$ (60,708)	$ (54,341)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	96,709	74,261	95,433	40,688
Net loss per share attributable to common stockholders, basic and diluted (in usd per share)	$ (0.18)	$ (0.28)	$ (0.64)	$ (1.34)

Net Loss Per Share Attributable to Common Stockholders - Schedule of Potentially Dilutive Securities (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	17,460	21,544	17,460	21,544
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	13,942	19,387	13,942	19,387
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2,860	1,050	2,860	1,050
Restricted shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	594	989	594	989
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	64	118	64	118

Geographic Information - Narrative (Details) - segment	3 Months Ended		9 Months Ended
Geographic Information - Narrative (Details) - segment	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Concentration Risk [Line Items]
Number of operating segments			1
United States \| Revenue \| Geographic concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage	63.00%	66.00%	64.00%	67.00%

Geographic Information - Revenue by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 91,852	$ 69,440	$ 257,537	$ 192,139
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	62,413	49,391	177,392	137,868
Europe, Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	19,968	14,002	56,123	38,218
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 9,471	$ 6,047	$ 24,022	$ 16,053

Geographic Information - Property And Equipment, Net By Geographic Area (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 18,525	$ 11,348
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	13,612	6,487
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 4,913	$ 4,861

Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2019	Nov. 08, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-38600
Entity Registrant Name	TENABLE HOLDINGS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-5580846
Entity Address, Address Line One	7021 Columbia Gateway Drive
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Columbia
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21046
City Area Code	410
Local Phone Number	872-0555
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	TENB
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		98,187,608
Entity Central Index Key	0001660280
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Ex Transition Period	true

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 171,303	$ 165,116
Short-term investments	125,333	118,119
Accounts receivable (net of allowance for doubtful accounts of $557 and $188 at September 30, 2019 and December 31, 2018, respectively)	81,201	68,261
Deferred commissions	26,030	23,272
Prepaid expenses and other current assets	21,126	22,020
Total current assets	424,993	396,788
Property and equipment, net	18,525	11,348
Deferred commissions (net of current portion)	38,493	36,162
Operating lease right-of-use assets	40,346	8,504
Other assets	9,855	7,810
Total assets	532,212	460,612
Current liabilities:
Accounts payable	795	171
Accrued expenses	9,474	5,554
Accrued compensation	24,244	29,594
Deferred revenue	245,985	213,644
Operating lease liabilities	3,970	4,262
Other current liabilities	701	1,079
Total current liabilities	285,169	254,304
Deferred revenue (net of current portion)	83,390	76,259
Operating lease liabilities (net of current portion)	37,788	6,055
Other liabilities	2,677	2,231
Total liabilities	409,024	338,849
Stockholders’ equity:
Common stock (par value: $0.01; 500,000 shares authorized; 97,960 and 93,126 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively)	980	931
Additional paid-in capital	648,964	586,940
Accumulated other comprehensive income	60	0
Accumulated deficit	(526,816)	(466,108)
Total stockholders’ equity	123,188	121,763
Total liabilities and stockholders’ equity	$ 532,212	$ 460,612

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 557	$ 188
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	97,960,000	93,126,000
Common stock, shares outstanding (in shares)	97,960,000	93,126,000

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 91,852	$ 69,440	$ 257,537	$ 192,139
Cost of revenue	15,245	12,161	42,389	30,768
Gross profit	76,607	57,279	215,148	161,371
Operating expenses:
Sales and marketing	56,699	44,550	165,403	125,964
Research and development	20,763	20,553	64,396	55,529
General and administrative	17,472	13,272	48,595	32,868
Total operating expenses	94,934	78,375	278,394	214,361
Loss from operations	(18,327)	(21,096)	(63,246)	(52,990)
Interest income, net	1,527	894	4,677	845
Other expense, net	(240)	(185)	(576)	(605)
Loss before income taxes	(17,040)	(20,387)	(59,145)	(52,750)
Provision for income taxes	600	482	1,563	1,157
Net loss	(17,640)	(20,869)	(60,708)	(53,907)
Accretion of Series A and B redeemable convertible preferred stock	0	(55)	0	(434)
Net loss attributable to common stockholders	$ (17,640)	$ (20,924)	$ (60,708)	$ (54,341)
Net loss per share attributable to common stockholders, basic and diluted (in usd per share)	$ (0.18)	$ (0.28)	$ (0.64)	$ (1.34)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	96,709	74,261	95,433	40,688

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (17,640)	$ (20,869)	$ (60,708)	$ (53,907)
Other comprehensive (loss) income, net of tax:
Unrealized (losses) gains on available-for-sale securities	(20)	0	60	0
Other comprehensive (loss) income	(20)	0	60	0
Comprehensive loss	$ (17,660)	$ (20,869)	$ (60,648)	$ (53,907)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock
Balance (in shares) at Dec. 31, 2017						15,848	39,538
Balance at Dec. 31, 2017						$ 49,935	$ 227,800
Redeemable Convertible Preferred Stock [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock						$ 13	$ 421
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)						(15,848)	(39,538)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering						$ (49,948)	$ (228,221)
Balance (in shares) at Sep. 30, 2018						0	0
Balance at Sep. 30, 2018						$ 0	$ 0
Balance (in shares) at Dec. 31, 2017		24,472
Balance at Dec. 31, 2017	$ (371,665)	$ 246	$ 20,676	$ 0	$ (392,587)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock	(434)		(434)
Exercise of stock options (in shares)		654
Exercise of stock options	1,415	$ 6	1,409
Repurchase of common stock (in shares)		(7)
Repurchase of common stock	(75)	$ (1)	(74)
Stock-based compensation	14,259		14,259
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses (in shares)		12,535
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses	264,799	$ 125	264,674
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)		55,386
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	278,169	$ 554	277,615
Other comprehensive income	0
Net loss	(53,907)				(53,907)
Balance (in shares) at Sep. 30, 2018		93,040
Balance at Sep. 30, 2018	132,561	$ 930	578,125	0	(446,494)
Balance (in shares) at Jun. 30, 2018						15,848	39,538
Balance at Jun. 30, 2018						$ 49,946	$ 228,168
Redeemable Convertible Preferred Stock [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock						$ 2	$ 53
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)						(15,848)	(39,538)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering						$ (49,948)	$ (228,221)
Balance (in shares) at Sep. 30, 2018						0	0
Balance at Sep. 30, 2018						$ 0	$ 0
Balance (in shares) at Jun. 30, 2018		24,951
Balance at Jun. 30, 2018	(398,724)	$ 250	26,651	0	(425,625)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Accretion of Series A and B redeemable convertible preferred stock	(55)		(55)
Exercise of stock options (in shares)		168
Exercise of stock options	405	$ 1	404
Stock-based compensation	8,836		8,836
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses (in shares)		12,535
Issuance of common stock in connection with initial public offering, net of underwriting discounts and commissions and other offering expenses	264,799	$ 125	264,674
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)		55,386
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	278,169	$ 554	277,615
Other comprehensive income	0
Net loss	(20,869)				(20,869)
Balance (in shares) at Sep. 30, 2018		93,040
Balance at Sep. 30, 2018	$ 132,561	$ 930	578,125	0	(446,494)
Balance (in shares) at Dec. 31, 2018						0	0
Balance at Dec. 31, 2018						$ 0	$ 0
Balance (in shares) at Sep. 30, 2019						0	0
Balance at Sep. 30, 2019						$ 0	$ 0
Balance (in shares) at Dec. 31, 2018	93,126	93,126
Balance at Dec. 31, 2018	$ 121,763	$ 931	586,940	0	(466,108)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Exercise of stock options (in shares)	3,625	3,625
Exercise of stock options	$ 15,448	$ 36	15,412
Vesting of restricted stock units (in shares)		432
Vesting of restricted stock units	0	$ 5	(5)
Issuance of common stock under employee stock purchase plan (in shares)		777
Issuance of common stock under employee stock purchase plan	15,129	$ 8	15,121
Stock-based compensation	31,496		31,496
Other comprehensive income	60			60
Net loss	$ (60,708)				(60,708)
Balance (in shares) at Sep. 30, 2019	97,960	97,960
Balance at Sep. 30, 2019	$ 123,188	$ 980	648,964	60	(526,816)
Balance (in shares) at Jun. 30, 2019						0	0
Balance at Jun. 30, 2019						$ 0	$ 0
Balance (in shares) at Sep. 30, 2019						0	0
Balance at Sep. 30, 2019						$ 0	$ 0
Balance (in shares) at Jun. 30, 2019		96,808
Balance at Jun. 30, 2019	120,959	$ 968	629,087	80	(509,176)
Increase (Decrease) in Stockholders' Deficit [Roll Forward]
Exercise of stock options (in shares)		383
Exercise of stock options	2,721	$ 4	2,717
Vesting of restricted stock units (in shares)		431
Vesting of restricted stock units	0	$ 5	(5)
Issuance of common stock under employee stock purchase plan (in shares)		338
Issuance of common stock under employee stock purchase plan	6,550	$ 3	6,547
Stock-based compensation	10,618		10,618
Other comprehensive income	(20)			(20)
Net loss	$ (17,640)				(17,640)
Balance (in shares) at Sep. 30, 2019	97,960	97,960
Balance at Sep. 30, 2019	$ 123,188	$ 980	$ 648,964	$ 60	$ (526,816)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (60,708)	$ (53,907)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,604	4,580
Stock-based compensation	31,191	14,206
Other	(787)	771
Changes in operating assets and liabilities:
Accounts receivable	(13,309)	(8,190)
Prepaid expenses and other current assets	820	941
Deferred commissions	(5,089)	(2,708)
Other assets	(2,386)	315
Accounts payable and accrued expenses	3,892	1,930
Accrued compensation	(5,350)	1,252
Deferred revenue	39,472	39,880
Other current liabilities	(195)	(4)
Other liabilities	173	(71)
Net cash used in operating activities	(7,672)	(1,005)
Cash flows from investing activities:
Purchases of property and equipment	(10,262)	(4,140)
Purchases of short-term investments	(179,703)	(34,114)
Sales and maturities of short-term investments	174,485	0
Net cash used in investing activities	(15,480)	(38,254)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting discounts and commissions	0	268,531
Payments of costs related to initial public offering	0	(3,732)
Principal payments under finance lease obligations	(12)	(389)
Proceeds from stock issued in connection with the employee stock purchase plan	15,129	0
Proceeds from the exercise of stock options	15,448	1,415
Repurchases of common stock	0	(75)
Net cash provided by financing activities	30,565	265,750
Effect of exchange rate changes on cash and cash equivalents and restricted cash	(1,226)	(675)
Net increase in cash and cash equivalents and restricted cash	6,187	225,816
Cash and cash equivalents and restricted cash at beginning of period	165,378	27,472
Cash and cash equivalents and restricted cash at end of period	171,565	253,288
Supplemental disclosure of cash flow information:
Cash paid for interest	73	85
Cash paid for income taxes	1,507	920
Supplemental cash flow information related to leases:
Operating cash payments for operating leases	3,297	3,098
Operating cash payments for finance leases	5	29
Supplemental disclosure of non-cash investing and financing activities:
Asset retirement obligations	$ 121	$ 67

Business and Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Business and Summary of Significant Accounting Policies

Business Description

Basis of Presentation

The results for the nine months ended September 30, 2019 are not necessarily indicative of the operating results expected for the year ending December 31, 2019 or any other future period.

Initial Public Offering

Use of Estimates

Revenue Recognition

•Identify the contract with a customer

•Identify the performance obligations in the contract

•Determine the transaction price

•Allocate the transaction price to the performance obligations in the contract

•Recognize revenue when or as performance obligations are satisfied

The following table presents a summary of revenue:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Subscription revenue	$	75,503	$	53,511	$	209,610	$	146,568
Perpetual license and maintenance revenue	13,797		13,864		40,877		40,753
Professional services and other revenue	2,552		2,065		7,050		4,818
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Subscription Revenue

Perpetual License and Maintenance Revenue

Professional Services and Other Revenue

Contracts with Multiple Performance Obligations

Variable Consideration

Concentrations

Contract Balances

Remaining Performance Obligations

Investments

other comprehensive income within stockholders’ equity (deficit). We periodically review our investment portfolio to determine whether investments have indicators of possible impairment.

Deferred Commissions

The following summarizes the activity of deferred incremental costs of obtaining a contract in the periods presented:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands)	2019			2018			2019			2018
Beginning balance	$	61,866		$	50,805		$	59,434		$	50,176
Capitalization of contract acquisition costs	9,612			7,138			24,846			16,985
Amortization of deferred contract acquisition costs	(6,955		)	(5,059		)	(19,757		)	(14,277		)
Ending balance	$	64,523		$	52,884		$	64,523		$	52,884

Amortization of deferred contract acquisition costs is included in sales and marketing expense in the consolidated statements of operations.

Leases

Lease expense for lease payments is recognized on a straight-line basis over the term of the lease.

Recent Accounting Pronouncements Not Yet Adopted

Cash and Cash Equivalents and Short-Term Investments

9 Months Ended

Sep. 30, 2019

Cash and Cash Equivalents [Abstract]

Cash and Cash Equivalents and Short-Term Investments

The following tables summarize the amortized cost, unrealized gain and loss and estimated fair value of cash equivalents and short-term investments:



	September 30, 2019
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Cash equivalents:
Money market funds	$	28,043	$	—	$	—		$	28,043
Commercial paper	4,496		—		—			4,496
Total cash equivalents	$	32,539	$	—	$	—		$	32,539

Short-term investments:
Commercial paper	$	56,754	$	—	$	—		$	56,754
Corporate bonds	15,993		32		—			16,025
U.S. Treasury and agency obligations	52,526		35		(7		)	52,554
Total short-term investments	$	125,273	$	67	$	(7	)	$	125,333



	December 31, 2018
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Cash equivalents:
Money market funds	$	38,022	$	—	$	—	$	38,022
Total cash equivalents	$	38,022	$	—	$	—	$	38,022

Short-term investments:
Commercial paper	$	79,634	$	—	$	—	$	79,634
Corporate bonds	16,119		—		—		16,119
U.S. Treasury and agency obligations	22,366		—		—		22,366
Total short-term investments	$	118,119	$	—	$	—	$	118,119

At September 30, 2019 and December 31, 2018, all of our short-term investments had maturities within the next twelve months.

Fair Value Measurements

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements


•	Level 1 — Quoted prices in active markets for identical assets and liabilities;


•	Level 2 — Observable inputs including quoted market prices for similar assets and liabilities in active markets, quoted prices for identical assets and liabilities in inactive markets, or inputs that are corroborated by observable market data; and


•	Level 3 — Unobservable inputs.

The following tables summarize assets that are measured at fair value on a recurring basis:



	September 30, 2019
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	28,043	$	—	$	—	$	28,043
Commercial paper	—		4,496		—		4,496
	$	28,043	$	4,496	$	—	$	32,539

Short-term investments
Commercial paper	$	—	$	56,754	$	—	$	56,754
Corporate bonds	—		16,025		—		16,025
U.S. Treasury and agency obligations	—		52,554		—		52,554
	$	—	$	125,333	$	—	$	125,333



	December 31, 2018
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	38,022	$	—	$	—	$	38,022
	$	38,022	$	—	$	—	$	38,022

Short-term investments
Commercial paper	$	—	$	79,634	$	—	$	79,634
Corporate bonds	—		16,119		—		16,119
U.S. Treasury and agency obligations	—		22,366		—		22,366
	$	—	$	118,119	$	—	$	118,119

We did not have any liabilities measured and recorded at fair value at September 30, 2019 or December 31, 2018.

- Definition

+ References + Details

Property and Equipment, Net

9 Months Ended

Sep. 30, 2019

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

Property and equipment, net consisted of the following:



(in thousands)	September 30, 2019			December 31, 2018
Computer software and equipment	$	20,221		$	13,038
Furniture and fixtures	3,738			2,376
Leasehold improvements	9,230			7,266
Right-of-use assets under finance leases	1,866			1,854
Total	35,055			24,534
Less: accumulated depreciation and amortization	(16,530		)	(13,186		)
Property and equipment, net	$	18,525		$	11,348

Leases

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Leases

The components of lease expense were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Operating lease cost	$	1,763	$	960	$	3,844	$	2,730

Finance lease cost
Amortization of ROU assets	$	157	$	155	$	465	$	459
Interest on lease liabilities	2		10		5		29
Total finance lease cost	$	159	$	165	$	470	$	488

Rent expense for short-term leases in the three and nine months ended September 30, 2019 and 2018 was not material.

Supplemental information related to leases was as follows:



	September 30, 2019	December 31, 2018
Operating leases
Weighted average remaining lease term	10.2 years	3.1 years
Weighted average discount rate	5.9%	7.1%



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
ROU assets obtained in exchange for lease obligations
Operating leases	$	32,292	$	263	$	34,490	$	1,525
Finance leases	—		4		11		4

Maturities of operating lease liabilities at September 30, 2019 were as follows:



(in thousands)
Year ending December 31,
2019⁽¹⁾	$	994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589		)
Less: Tenant incentives	(14,013		)
Total	$	41,758

_______________

(1) Represents the three months ending December 31, 2019.

Leases

The components of lease expense were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Operating lease cost	$	1,763	$	960	$	3,844	$	2,730

Finance lease cost
Amortization of ROU assets	$	157	$	155	$	465	$	459
Interest on lease liabilities	2		10		5		29
Total finance lease cost	$	159	$	165	$	470	$	488

Rent expense for short-term leases in the three and nine months ended September 30, 2019 and 2018 was not material.

Supplemental information related to leases was as follows:



	September 30, 2019	December 31, 2018
Operating leases
Weighted average remaining lease term	10.2 years	3.1 years
Weighted average discount rate	5.9%	7.1%



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
ROU assets obtained in exchange for lease obligations
Operating leases	$	32,292	$	263	$	34,490	$	1,525
Finance leases	—		4		11		4

Maturities of operating lease liabilities at September 30, 2019 were as follows:



(in thousands)
Year ending December 31,
2019⁽¹⁾	$	994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589		)
Less: Tenant incentives	(14,013		)
Total	$	41,758

_______________

(1) Represents the three months ending December 31, 2019.

Debt	9 Months Ended
Debt	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	Debt On May 4, 2017, we entered into a $25.0 million revolving credit facility (“Credit Facility”) with Silicon Valley Bank, which is available for use until May 4, 2020. There were no borrowings under the Credit Facility during the nine months ended September 30, 2019 or in 2018.

Redeemable Convertible Preferred Stock and Common Stock	9 Months Ended
Redeemable Convertible Preferred Stock and Common Stock	Sep. 30, 2019
Stockholders' Equity Note [Abstract]
Redeemable Convertible Preferred Stock and Common Stock	Redeemable Convertible Preferred Stock and Common Stock Redeemable Convertible Preferred Stock In October 2012, Tenable, Inc. (now a wholly owned subsidiary of Tenable Holdings, Inc.) issued 15,847,500 shares of Series A redeemable convertible preferred stock. In December 2015, we issued 15,847,500 shares, par value of $0.01, of Series A redeemable convertible preferred stock ("Series A") in exchange for Series A redeemable convertible preferred stock of Tenable, Inc. in connection with a recapitalization. This exchange was made on a one for one basis. In addition, we authorized 42,000,000 shares and issued 39,538,354 shares, par value of $0.01, of Series B redeemable convertible preferred stock ("Series B"). Upon completion of our IPO, Series A and Series B (together, the “Redeemable Convertible Preferred Stock”) automatically converted into an aggregate of 55,385,854 shares of our common stock. We accreted the Redeemable Convertible Preferred Stock to the redemption price at the redemption date using the effective interest method. Upon completion of our IPO, the accretion rights of the Redeemable Convertible Preferred Stock were terminated. Upon the completion of our IPO, we filed an Amended and Restated Certificate of Incorporation, authorizing a total of 500,000,000 shares of common stock and 10,000,000 shares of preferred stock. There were no shares of preferred stock issued or outstanding at September 30, 2019 or December 31, 2018. Common Stock The voting, dividend, and liquidation rights of common stockholders are subject to, and qualified by, the rights of preferred stockholders. The common stockholders are entitled to receive dividends when, as and if, declared by the Board of Directors, subject to preferential dividend rights of preferred stockholders. Upon dissolution or liquidation, our common stockholders will be entitled to receive all assets available for distribution to stockholders, subject to any preferential rights of preferred stockholders.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Stock-based compensation expense included in the consolidated statements of operations was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Cost of revenue	$	694	$	692	$	2,088	$	883
Sales and marketing	3,521		2,707		11,102		3,984
Research and development	2,124		2,427		6,595		3,594
General and administrative	4,160		2,957		11,406		5,745
Total stock-based compensation expense	$	10,499	$	8,783	$	31,191	$	14,206

Stock Options

A summary of our stock option activity is presented below:



(in thousands, except for per share data and years)	Number of Shares	Weighted Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2018	19,219	$	7.78	8.0	$	277,114
Granted	—	—
Exercised	(3,625)	4.26
Forfeited/canceled	(1,652)	10.03
Outstanding at September 30, 2019	13,942	8.43		7.5	194,654
Exercisable at September 30, 2019	6,470	5.80		6.7	107,297

At September 30, 2019, there were 13.9 million stock options that were vested and expected to vest.

Restricted Stock and Restricted Stock Units

A summary of our restricted stock and restricted stock units activity is presented below:



	Restricted Stock				Restricted Stock Units
(in thousands, except for per share data)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value
Unvested balance at December 31, 2018	890		$	4.25	1,129		$	18.90
Granted	—		—		2,454		28.10
Vested	(296	)	4.25		(432	)	17.20
Forfeited	—		—		(291	)	23.96
Unvested balance at September 30, 2019	594		4.25		2,860		26.54

2018 Employee Stock Purchase Plan

In the nine months ended September 30, 2019, employees purchased 776,809 shares of our common stock at a weighted average price of $19.48 per share, resulting in cash proceeds to us of $15.1 million.

The fair value of the 2018 ESPP purchase rights was estimated on the grant date using a Black-Scholes option-pricing model and the following assumptions:



Expected term (in years)	0.5 — 2.1
Expected volatility	31.9% — 44.6%
Risk-free interest rate	1.5% — 2.7%
Expected dividend yield	—

Net Loss Per Share Attributable to Common Stockholders

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except per share data)	2019			2018			2019			2018
Net loss attributable to common stockholders	$	(17,640	)	$	(20,924	)	$	(60,708	)	$	(54,341	)

Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted	96,709			74,261			95,433			40,688
Net loss per share attributable to common stockholders, basic and diluted	$	(0.18	)	$	(0.28	)	$	(0.64	)	$	(1.34	)

The following potentially dilutive securities have been excluded from the diluted per share calculations because they would have been antidilutive:



	Three and Nine Months Ended September 30,
(in thousands)	2019	2018
Stock options	13,942	19,387
Restricted stock units	2,860	1,050
Restricted shares	594	989
Shares to be issued under the 2018 ESPP	64	118
Total	17,460	21,544

Geographic Information

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Geographic Information

Revenue by region, based on the address of the end user as specified in our subscription, license or service agreements, was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Americas	$	62,413	$	49,391	$	177,392	$	137,868
Europe, Middle East and Africa	19,968		14,002		56,123		38,218
Asia Pacific	9,471		6,047		24,022		16,053
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Our property and equipment, net by geographic area is summarized as follows:



(in thousands)	September 30, 2019		December 31, 2018
United States	$	13,612	$	6,487
International	4,913		4,861
Property and equipment, net	$	18,525	$	11,348

Business and Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

•Identify the contract with a customer

•Identify the performance obligations in the contract

•Determine the transaction price

•Allocate the transaction price to the performance obligations in the contract

•Recognize revenue when or as performance obligations are satisfied

The following table presents a summary of revenue:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Subscription revenue	$	75,503	$	53,511	$	209,610	$	146,568
Perpetual license and maintenance revenue	13,797		13,864		40,877		40,753
Professional services and other revenue	2,552		2,065		7,050		4,818
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Subscription Revenue

Perpetual License and Maintenance Revenue

Professional Services and Other Revenue

Contracts with Multiple Performance Obligations

Variable Consideration

Concentrations

Contract Balances

We generally bill our customers in advance and accounts receivable are recorded when we have the right to invoice the customer.

Investments

other comprehensive income within stockholders’ equity (deficit). We periodically review our investment portfolio to determine whether investments have indicators of possible impairment.

Leases

Lease expense for lease payments is recognized on a straight-line basis over the term of the lease.

Recent Accounting Pronouncements Not Yet Adopted

Business and Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of revenue

The following table presents a summary of revenue:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Subscription revenue	$	75,503	$	53,511	$	209,610	$	146,568
Perpetual license and maintenance revenue	13,797		13,864		40,877		40,753
Professional services and other revenue	2,552		2,065		7,050		4,818
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Activity of deferred contract costs

The following summarizes the activity of deferred incremental costs of obtaining a contract in the periods presented:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands)	2019			2018			2019			2018
Beginning balance	$	61,866		$	50,805		$	59,434		$	50,176
Capitalization of contract acquisition costs	9,612			7,138			24,846			16,985
Amortization of deferred contract acquisition costs	(6,955		)	(5,059		)	(19,757		)	(14,277		)
Ending balance	$	64,523		$	52,884		$	64,523		$	52,884

Cash and Cash Equivalents and Short-Term Investments (Tables)

9 Months Ended

Sep. 30, 2019

Cash and Cash Equivalents [Abstract]

Summary of amortized cost, unrealized gain and loss and estimated fair value

The following tables summarize the amortized cost, unrealized gain and loss and estimated fair value of cash equivalents and short-term investments:



	September 30, 2019
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Cash equivalents:
Money market funds	$	28,043	$	—	$	—		$	28,043
Commercial paper	4,496		—		—			4,496
Total cash equivalents	$	32,539	$	—	$	—		$	32,539

Short-term investments:
Commercial paper	$	56,754	$	—	$	—		$	56,754
Corporate bonds	15,993		32		—			16,025
U.S. Treasury and agency obligations	52,526		35		(7		)	52,554
Total short-term investments	$	125,273	$	67	$	(7	)	$	125,333



	December 31, 2018
(in thousands)	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Cash equivalents:
Money market funds	$	38,022	$	—	$	—	$	38,022
Total cash equivalents	$	38,022	$	—	$	—	$	38,022

Short-term investments:
Commercial paper	$	79,634	$	—	$	—	$	79,634
Corporate bonds	16,119		—		—		16,119
U.S. Treasury and agency obligations	22,366		—		—		22,366
Total short-term investments	$	118,119	$	—	$	—	$	118,119

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Schedule of assets measured at fair value on recurring basis

The following tables summarize assets that are measured at fair value on a recurring basis:



	September 30, 2019
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	28,043	$	—	$	—	$	28,043
Commercial paper	—		4,496		—		4,496
	$	28,043	$	4,496	$	—	$	32,539

Short-term investments
Commercial paper	$	—	$	56,754	$	—	$	56,754
Corporate bonds	—		16,025		—		16,025
U.S. Treasury and agency obligations	—		52,554		—		52,554
	$	—	$	125,333	$	—	$	125,333



	December 31, 2018
(in thousands)	Level 1		Level 2		Level 3		Total
Cash and cash equivalents
Money market funds	$	38,022	$	—	$	—	$	38,022
	$	38,022	$	—	$	—	$	38,022

Short-term investments
Commercial paper	$	—	$	79,634	$	—	$	79,634
Corporate bonds	—		16,119		—		16,119
U.S. Treasury and agency obligations	—		22,366		—		22,366
	$	—	$	118,119	$	—	$	118,119

- Definition

+ References + Details

Property and Equipment, Net (Tables)

9 Months Ended

Sep. 30, 2019

Property, Plant and Equipment [Abstract]

Property and equipment, net

Property and equipment, net consisted of the following:



(in thousands)	September 30, 2019			December 31, 2018
Computer software and equipment	$	20,221		$	13,038
Furniture and fixtures	3,738			2,376
Leasehold improvements	9,230			7,266
Right-of-use assets under finance leases	1,866			1,854
Total	35,055			24,534
Less: accumulated depreciation and amortization	(16,530		)	(13,186		)
Property and equipment, net	$	18,525		$	11,348

Leases (Tables)

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Components of leases

Supplemental information related to leases was as follows:



	September 30, 2019	December 31, 2018
Operating leases
Weighted average remaining lease term	10.2 years	3.1 years
Weighted average discount rate	5.9%	7.1%



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
ROU assets obtained in exchange for lease obligations
Operating leases	$	32,292	$	263	$	34,490	$	1,525
Finance leases	—		4		11		4

The components of lease expense were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Operating lease cost	$	1,763	$	960	$	3,844	$	2,730

Finance lease cost
Amortization of ROU assets	$	157	$	155	$	465	$	459
Interest on lease liabilities	2		10		5		29
Total finance lease cost	$	159	$	165	$	470	$	488

Schedule of maturities of operating lease liabilities

Maturities of operating lease liabilities at September 30, 2019 were as follows:



(in thousands)
Year ending December 31,
2019⁽¹⁾	$	994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589		)
Less: Tenant incentives	(14,013		)
Total	$	41,758

_______________

(1) Represents the three months ending December 31, 2019.

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Stock-based compensation expense

Stock-based compensation expense included in the consolidated statements of operations was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Cost of revenue	$	694	$	692	$	2,088	$	883
Sales and marketing	3,521		2,707		11,102		3,984
Research and development	2,124		2,427		6,595		3,594
General and administrative	4,160		2,957		11,406		5,745
Total stock-based compensation expense	$	10,499	$	8,783	$	31,191	$	14,206

Stock option activity

A summary of our stock option activity is presented below:



(in thousands, except for per share data and years)	Number of Shares	Weighted Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2018	19,219	$	7.78	8.0	$	277,114
Granted	—	—
Exercised	(3,625)	4.26
Forfeited/canceled	(1,652)	10.03
Outstanding at September 30, 2019	13,942	8.43		7.5	194,654
Exercisable at September 30, 2019	6,470	5.80		6.7	107,297

Summary of restricted stock and restricted stock units

A summary of our restricted stock and restricted stock units activity is presented below:



	Restricted Stock				Restricted Stock Units
(in thousands, except for per share data)	Number of Shares		Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value
Unvested balance at December 31, 2018	890		$	4.25	1,129		$	18.90
Granted	—		—		2,454		28.10
Vested	(296	)	4.25		(432	)	17.20
Forfeited	—		—		(291	)	23.96
Unvested balance at September 30, 2019	594		4.25		2,860		26.54

ESPP valuation assumptions

The fair value of the 2018 ESPP purchase rights was estimated on the grant date using a Black-Scholes option-pricing model and the following assumptions:



Expected term (in years)	0.5 — 2.1
Expected volatility	31.9% — 44.6%
Risk-free interest rate	1.5% — 2.7%
Expected dividend yield	—

Net Loss Per Share Attributable to Common Stockholders (Tables)

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Computation of basic and diluted net loss per share

The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders:



	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except per share data)	2019			2018			2019			2018
Net loss attributable to common stockholders	$	(17,640	)	$	(20,924	)	$	(60,708	)	$	(54,341	)

Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted	96,709			74,261			95,433			40,688
Net loss per share attributable to common stockholders, basic and diluted	$	(0.18	)	$	(0.28	)	$	(0.64	)	$	(1.34	)

Potentially dilutive securities

The following potentially dilutive securities have been excluded from the diluted per share calculations because they would have been antidilutive:



	Three and Nine Months Ended September 30,
(in thousands)	2019	2018
Stock options	13,942	19,387
Restricted stock units	2,860	1,050
Restricted shares	594	989
Shares to be issued under the 2018 ESPP	64	118
Total	17,460	21,544

Geographic Information (Tables)

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Revenue by region

Revenue by region, based on the address of the end user as specified in our subscription, license or service agreements, was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2019		2018		2019		2018
Americas	$	62,413	$	49,391	$	177,392	$	137,868
Europe, Middle East and Africa	19,968		14,002		56,123		38,218
Asia Pacific	9,471		6,047		24,022		16,053
Revenue	$	91,852	$	69,440	$	257,537	$	192,139

Property and equipment, net by geographic area

Our property and equipment, net by geographic area is summarized as follows:



(in thousands)	September 30, 2019		December 31, 2018
United States	$	13,612	$	6,487
International	4,913		4,861
Property and equipment, net	$	18,525	$	11,348

Business and Summary of Significant Accounting Policies - Initial Public Offering (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended	9 Months Ended
	Jul. 30, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, authorized (in shares)	500,000,000			500,000,000	500,000,000
Preferred stock, authorized (in shares)	10,000,000
IPO
Class of Stock [Line Items]
Stock sold, price per share (in usd per share)	$ 23.00
Net proceeds from sale of stock	$ 264.6
Common Stock
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)		55,386,000	55,386,000
Common Stock \| IPO
Class of Stock [Line Items]
Stock sold (in shares)	12,535,000
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	55,385,854
Common Stock \| Over-allotment option
Class of Stock [Line Items]
Stock sold (in shares)	1,635,000
Redeemable convertible Series A preferred stock \| IPO
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	15,847,500
Redeemable convertible Series B preferred stock \| IPO
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	39,538,354

Business and Summary of Significant Accounting Policies - Summary of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 91,852	$ 69,440	$ 257,537	$ 192,139
Subscription revenue
Disaggregation of Revenue [Line Items]
Revenue	75,503	53,511	209,610	146,568
Perpetual license and maintenance revenue
Disaggregation of Revenue [Line Items]
Revenue	13,797	13,864	40,877	40,753
Professional services and other revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 2,552	$ 2,065	$ 7,050	$ 4,818

Business and Summary of Significant Accounting Policies - Perpetual License and Maintenance Revenue (Details) - Perpetual license and maintenance revenue	9 Months Ended
	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
License and maintenance period	1 year
Estimated maintenance renewal period	4 years
Economic life of perpetual license contracts	5 years

Business and Summary of Significant Accounting Policies - Concentrations (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
One distributor \| Revenue \| Customer concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage	43.00%	46.00%	43.00%	46.00%
One distributor \| Accounts receivable \| Customer concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage			40.00%		46.00%
Channel network \| Revenue \| Sales method risk
Concentration Risk [Line Items]
Concentration risk, percentage	91.00%	88.00%	90.00%	87.00%

Business and Summary of Significant Accounting Policies - Contract Balances (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue recognized that was included in deferred revenue	$ 84.6	$ 62.5	$ 184.3	$ 133.3

Business and Summary of Significant Accounting Policies - Remaining Performance Obligations (Details) $ in Millions	Sep. 30, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Future estimated revenue	$ 333.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected recognized percentage over succeeding 12 months	74.00%
Expected timing of satisfaction	4 years

Business and Summary of Significant Accounting Policies - Deferred Commissions (Details)	Sep. 30, 2019
Perpetual license and maintenance revenue
Capitalized Contract Cost [Line Items]
Estimated period of benefit	5 years
Minimum \| Subscription revenue
Capitalized Contract Cost [Line Items]
Estimated period of benefit	3 years
Maximum \| Subscription revenue
Capitalized Contract Cost [Line Items]
Estimated period of benefit	4 years

Business and Summary of Significant Accounting Policies - Activity of Deferred Contract Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Capitalized Contract Cost [Roll Forward]
Beginning balance	$ 61,866	$ 50,805	$ 59,434	$ 50,176
Capitalization of contract acquisition costs	9,612	7,138	24,846	16,985
Amortization of deferred contract acquisition costs	(6,955)	(5,059)	(19,757)	(14,277)
Ending balance	$ 64,523	$ 52,884	$ 64,523	$ 52,884

Cash and Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Restricted cash	$ 300	$ 300
Cash and Cash Equivalents [Line Items]
Amortized Cost	125,273	118,119
Unrealized Gain	67	0
Unrealized Loss	(7)	0
Estimated fair value	125,333	118,119
Commercial paper
Cash and Cash Equivalents [Line Items]
Amortized Cost	56,754	79,634
Unrealized Gain	0	0
Unrealized Loss	0	0
Estimated fair value	56,754	79,634
Corporate bonds
Cash and Cash Equivalents [Line Items]
Amortized Cost	15,993	16,119
Unrealized Gain	32	0
Unrealized Loss	0	0
Estimated fair value	16,025	16,119
U.S. Treasury and agency obligations
Cash and Cash Equivalents [Line Items]
Amortized Cost	52,526	22,366
Unrealized Gain	35	0
Unrealized Loss	(7)	0
Estimated fair value	52,554	22,366
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	28,043	38,022
Commercial paper
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	4,496
Cash equivalents
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 32,539	$ 38,022

Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total	$ 35,055		$ 35,055		$ 24,534
Less: accumulated depreciation and amortization	(16,530)		(16,530)		(13,186)
Property and equipment, net	18,525		18,525		11,348
Depreciation and amortization	1,400	$ 1,400	4,200	$ 4,100
Computer software and equipment
Property, Plant and Equipment [Line Items]
Total	20,221		20,221		13,038
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	3,738		3,738		2,376
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total	9,230		9,230		7,266
Right-of-use assets under finance leases
Property, Plant and Equipment [Line Items]
Total	$ 1,866		$ 1,866		$ 1,854

Leases - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
Leases - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Renewal term	5 years
Operating lease right-of-use assets	$ 40,346	$ 8,504
Lease liability	41,758
Lease payments expected to commence	$ 78,360
Minimum
Lessee, Lease, Description [Line Items]
Remaining term of leases	1 year
Options to terminate lease	3 years
Maximum
Lessee, Lease, Description [Line Items]
Remaining term of leases	12 years
Options to terminate lease	6 years
Columbia, Maryland
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 32,300
Lease liability	$ 32,000
Initial term of contract	147 months
Lease payments expected to commence	$ 67,700

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Operating lease cost	$ 1,763	$ 960	$ 3,844	$ 2,730
Amortization of ROU assets	157	155	465	459
Interest on lease liabilities	2	10	5	29
Total finance lease cost	$ 159	$ 165	$ 470	$ 488

Leases - Supplemental Information Related to Leases (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating leases
Weighted average remaining lease term	10 years 2 months 12 days		10 years 2 months 12 days		3 years 1 month 6 days
Weighted average discount rate	5.90%		5.90%		7.10%
ROU assets obtained in exchange for lease obligations
Operating leases	$ 32,292	$ 263	$ 34,490	$ 1,525
Finance leases	$ 0	$ 4	$ 11	$ 4

Leases - Operating Lease Liability Maturities (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Leases [Abstract]
2019	$ 994
2020	4,088
2021	7,348
2022	6,673
2023	6,658
Thereafter	52,599
Total lease payments	78,360
Less: Imputed interest	(22,589)
Less: Tenant incentives	(14,013)
Total	$ 41,758

Debt (Details) - USD ($)	9 Months Ended	12 Months Ended
Debt (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018	May 04, 2017
Line of Credit Facility [Line Items]
Borrowings outstanding		$ 0
Silicon Valley Bank
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity			$ 25,000,000.0
Borrowings outstanding	$ 0

Redeemable Convertible Preferred Stock and Common Stock (Details)		1 Months Ended		3 Months Ended	9 Months Ended
	Jul. 30, 2018 shares	Dec. 31, 2015 $ / shares shares	Oct. 31, 2012 shares	Sep. 30, 2018 shares	Sep. 30, 2018 shares	Sep. 30, 2019 shares	Dec. 31, 2018 shares
Class of Stock [Line Items]
Conversion ratio		1
Common stock, authorized (in shares)	500,000,000					500,000,000	500,000,000
Preferred stock, authorized (in shares)	10,000,000
Preferred stock, shares issued and outstanding (in shares)						0	0
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Stock sold (in shares)		15,847,500	15,847,500
Redeemable convertible preferred stock, par value (in usd per share) \| $ / shares		$ 0.01
Series B Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Stock sold (in shares)		39,538,354
Redeemable convertible preferred stock, par value (in usd per share) \| $ / shares		$ 0.01
Redeemable convertible preferred stock, shares authorized (in shares)		42,000,000
Common Stock
Class of Stock [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)				55,386,000	55,386,000
Common Stock \| IPO
Class of Stock [Line Items]
Stock sold (in shares)	12,535,000
Issuance of common stock upon conversion of redeemable convertible preferred stock (in shares)	55,385,854

Stock-Based Compensation - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense, outstanding stock options	$ 29.8
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares reserved for issuance	5.00%
Shares available for grant (in shares) \| shares	15,052,780
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, stock incentive plans, maximum term	10 years
Estimated remaining weighted average period	2 years 4 months 24 days
Stock options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	3 years
Stock options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	4 years
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated remaining weighted average period	1 year 3 months 18 days
Unrecognized stock-based compensation expense, unvested restricted stock or RSUs	$ 2.1
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated remaining weighted average period	3 years 2 months 12 days
Unrecognized stock-based compensation expense, unvested restricted stock or RSUs	$ 62.4
Restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	2 years
Restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan, vesting period	4 years

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 10,499	$ 8,783	$ 31,191	$ 14,206
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	694	692	2,088	883
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	3,521	2,707	11,102	3,984
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	2,124	2,427	6,595	3,594
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation	$ 4,160	$ 2,957	$ 11,406	$ 5,745

Stock-Based Compensation - Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Number of Shares
Number of shares outstanding, beginning of period (in shares) \| shares	19,219
Number of shares, granted (in shares) \| shares	0
Number of shares, exercised (in shares) \| shares	(3,625)
Number of shares, forfeited/canceled (in shares) \| shares	(1,652)
Number of shares outstanding, end of period (in shares) \| shares	13,942	19,219
Number of shares exercisable (in shares) \| shares	6,470
Weighted Average Exercise Price
Weighted average exercise price, outstanding, beginning of period (in USD per share) \| $ / shares	$ 7.78
Weighted average exercise price, granted (in USD per share) \| $ / shares	0
Weighted average exercise price, exercised (in USD per share) \| $ / shares	4.26
Weighted average exercise price, forfeited/canceled (in USD per share) \| $ / shares	10.03
Weighted average exercise price, outstanding, end of period (in USD per share) \| $ / shares	8.43	$ 7.78
Weighted average exercise price, exercisable (in USD per share) \| $ / shares	$ 5.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term (in years), outstanding	7 years 6 months	8 years
Weighted average remaining contractual term (in years), exercisable	6 years 8 months 12 days
Aggregate intrinsic value, outstanding \| $	$ 194,654	$ 277,114
Aggregate intrinsic value, exercisable \| $	$ 107,297

Stock-Based Compensation - Stock Option Activity (Narrative) (Details) shares in Millions	Sep. 30, 2019 shares
Share-based Payment Arrangement [Abstract]
Stock options vested and expected to vest (in shares)	13.9

Stock-Based Compensation - Restricted Stock and Restricted Stock Units (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2019 $ / shares shares
Restricted shares
Number of Shares
Number of shares unvested, beginning of period (in shares) \| shares	890
Number of shares, granted (in shares) \| shares	0
Number of shares, vested (in shares) \| shares	(296)
Number of shares, forfeited (in shares) \| shares	0
Number of shares unvested, end of period (in shares) \| shares	594
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning of period (in USD per share) \| $ / shares	$ 4.25
Weighted average grant date fair value, granted (in USD per share) \| $ / shares	0
Weighted average grant date fair value, vested (in USD per share) \| $ / shares	4.25
Weighted average grant date fair value, forfeited (in USD per share) \| $ / shares	0
Weighted average grant date fair value, end of period (in USD per share) \| $ / shares	$ 4.25
Restricted stock units
Number of Shares
Number of shares unvested, beginning of period (in shares) \| shares	1,129
Number of shares, granted (in shares) \| shares	2,454
Number of shares, vested (in shares) \| shares	(432)
Number of shares, forfeited (in shares) \| shares	(291)
Number of shares unvested, end of period (in shares) \| shares	2,860
Weighted Average Grant Date Fair Value
Weighted average grant date fair value, beginning of period (in USD per share) \| $ / shares	$ 18.90
Weighted average grant date fair value, granted (in USD per share) \| $ / shares	28.10
Weighted average grant date fair value, vested (in USD per share) \| $ / shares	17.20
Weighted average grant date fair value, forfeited (in USD per share) \| $ / shares	23.96
Weighted average grant date fair value, end of period (in USD per share) \| $ / shares	$ 26.54

Stock-Based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from stock issued in connection with the employee stock purchase plan	$ 15,129	$ 0
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares reserved for issuance	1.50%
Common stock, annual increase (in shares)	8,000,000
Common stock reserved for issuance (in shares)	4,620,087
Percentage of employee earnings allowed	15.00%
Discount price percentage	85.00%
Offering period (up to)	27 months
Common stock purchased (in shares)	776,809
Share price (in USD per share)	$ 19.48
Employee contributions	$ 1,500
Unrecognized stock-based compensation expense	$ 11,300
Remaining offering period	1 year 10 months 24 days

Stock-Based Compensation - Fair Value Assumptions (Details) - Employee stock purchase plan	9 Months Ended
	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	31.90%
Expected volatility, maximum	44.60%
Risk - free interest rate, minimum	1.50%
Risk - free interest rate, maximum	2.70%
Expected dividend yield	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	2 years 1 month 6 days

Net Loss Per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net loss attributable to common stockholders	$ (17,640)	$ (20,924)	$ (60,708)	$ (54,341)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	96,709	74,261	95,433	40,688
Net loss per share attributable to common stockholders, basic and diluted (in usd per share)	$ (0.18)	$ (0.28)	$ (0.64)	$ (1.34)

Net Loss Per Share Attributable to Common Stockholders - Schedule of Potentially Dilutive Securities (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	17,460	21,544	17,460	21,544
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	13,942	19,387	13,942	19,387
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2,860	1,050	2,860	1,050
Restricted shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	594	989	594	989
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	64	118	64	118

Geographic Information - Narrative (Details) - segment	3 Months Ended		9 Months Ended
Geographic Information - Narrative (Details) - segment	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Concentration Risk [Line Items]
Number of operating segments			1
United States \| Revenue \| Geographic concentration risk
Concentration Risk [Line Items]
Concentration risk, percentage	63.00%	66.00%	64.00%	67.00%

Geographic Information - Revenue by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 91,852	$ 69,440	$ 257,537	$ 192,139
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	62,413	49,391	177,392	137,868
Europe, Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	19,968	14,002	56,123	38,218
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 9,471	$ 6,047	$ 24,022	$ 16,053

Geographic Information - Property And Equipment, Net By Geographic Area (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 18,525	$ 11,348
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	13,612	6,487
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 4,913	$ 4,861

Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 125,333	$ 118,119
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	56,754	79,634
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	16,025	16,119
U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	52,554	22,366
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	28,043	38,022
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,496
Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	32,539	38,022
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 \| U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	28,043	38,022
Level 1 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Level 1 \| Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	28,043	38,022
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	125,333	118,119
Level 2 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	56,754	79,634
Level 2 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	16,025	16,119
Level 2 \| U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	52,554	22,366
Level 2 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Level 2 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,496
Level 2 \| Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4,496	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 \| U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Level 3 \| Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0
Level 3 \| Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 0	$ 0