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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	Apr. 30, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	QUALYS, INC.
Entity Central Index Key	0001107843
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		39,158,096

Condensed Consolidated Balance Sheets - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 93,127,000	$ 41,026,000
Short-term marketable securities	205,009,000	248,140,000
Accounts receivable, net of allowance of $653 and $683 as of March 31, 2019 and December 31, 2018, respectively	67,863,000	75,825,000
Prepaid expenses and other current assets	16,538,000	13,974,000
Total current assets	382,537,000	378,965,000
Long-term marketable securities	96,322,000	76,710,000
Property and equipment, net	60,486,000	61,442,000
Operating Lease, Right-of-Use Asset	29,604,000
Deferred tax assets, net	24,653,000	26,387,000
Intangible assets, net	21,356,000	21,976,000
Goodwill	7,325,000	7,225,000
Restricted cash	1,200,000	1,200,000
Other noncurrent assets	12,658,000	11,775,000
Total assets	636,141,000	585,680,000
Current liabilities :
Accounts payable	566,000	5,588,000
Accrued liabilities	32,017,000	25,130,000
Deferred revenues, current	174,452,000	164,624,000
Finance Lease, Liability, Current	1,153,000	1,565,000
Operating Lease, Liability, Noncurrent	33,589,000
Total current liabilities	208,188,000	196,907,000
Deferred revenues, noncurrent	20,450,000	20,423,000
Other noncurrent liabilities	511,000	10,361,000
Total liabilities	262,738,000	227,691,000
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 20,000,000 shares authorized, no shares issued and outstanding at March 31, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value; 1,000,000,000 shares authorized; 39,133,832 and 39,015,034 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	39,000	39,000
Additional paid-in capital	338,566,000	330,572,000
Accumulated other comprehensive income (loss)	310,000	(586,000)
Retained earnings	34,488,000	27,964,000
Total stockholders’ equity	373,403,000	357,989,000
Total liabilities and stockholders’ equity	$ 636,141,000	$ 585,680,000

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ 343,544	$ 39	$ 304,155	$ (574)	$ 39,924
Balance (in shares) at Dec. 31, 2017		38,598,117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	9,142				9,142
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(391)			(391)
Change in unrealized loss on investments	(391)
Issuance of common stock upon exercise of stock options	7,933		7,933
Issuance of common stock upon exercise of stock options (shares)		285,997
Stock Repurchased During Period, Shares		(21,288)
Treasury Stock, Value, Acquired, Cost Method	(1,481)		(255)		(1,226)
Issuance of common stock upon vesting of restricted stock units (in shares)		94,866
Taxes from release of the restricted share units	(4,030)		(4,030)
Stock-based compensation	8,891		8,891
Ending balance at Mar. 31, 2018	366,319	$ 39	316,694	(965)	50,551
Balance (in shares) at Mar. 31, 2018		38,957,692
Beginning balance at Dec. 31, 2017	$ 343,544	$ 39	304,155	(574)	39,924
Balance (in shares) at Dec. 31, 2017		38,598,117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (shares)	152,164
Accumulated deficit	$ 27,964
Beginning balance at Dec. 31, 2018	357,989	$ 39	330,572	(586)	27,964
Balance (in shares) at Dec. 31, 2018		39,015,034
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,266				13,266
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	896			896
Change in unrealized loss on investments	683
Issuance of common stock upon exercise of stock options	4,047		4,047
Issuance of common stock upon exercise of stock options (shares)		152,164
Stock Repurchased During Period, Shares		(94,090)
Treasury Stock, Value, Acquired, Cost Method	(7,871)		(1,129)		(6,742)
Issuance of common stock upon vesting of restricted stock units (in shares)		99,601
Taxes from release of the restricted share units	(3,367)		(3,367)
Stock-based compensation	8,443		8,443
Ending balance at Mar. 31, 2019	373,403	$ 39	$ 338,566	$ 310	$ 34,488
Balance (in shares) at Mar. 31, 2019		39,133,832
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated deficit	$ 34,488

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 653	$ 816
Preferred stock, par or stated value per share (USD per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par or stated value per share (USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	39,133,832	38,598,117
Common stock, shares outstanding	39,133,832	38,598,117

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues
Revenues	$ 75,343	$ 64,878
Cost of revenues	17,709	15,901
Gross profit	57,634	48,977
Operating expenses:
Research and development	15,837	12,553
Sales and marketing	17,315	16,233
General and administrative	10,431	11,785
Total operating expenses	43,583	40,571
Income from operations	14,051	8,406
Other income (expense), net:
Interest expense	(42)	(38)
Interest income	2,051	1,090
Other income (expense), net	(223)	193
Total other income, net	1,786	1,245
Income before income taxes	15,837	9,651
Provision for income taxes	2,571	509
Net income	$ 13,266	$ 9,142
Net income per share:
Basic (USD per share)	$ 0.34	$ 0.24
Diluted (USD per share)	$ 0.32	$ 0.22
Weighted average shares used in computing net income per share:
Basic (shares)	39,109	38,789
Diluted (shares)	41,546	41,934

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 13,266	$ 9,142
Available-for-sale marketable securities:
Change in net unrealized gain (loss) on marketable securities, net of tax	655	(407)
Reclassification adjustment for net realized gain included in net income, net of tax	28	16
Total change in unrealized gain (loss) on marketable securities, net of tax	683	(391)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	213	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	896	(391)
Comprehensive income	$ 14,162	$ 8,751

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 13,266	$ 9,142
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	7,935	7,043
Loss on disposal of property and equipment	105	7
Stock-based compensation	8,445	8,891
Amortization of premiums and accretion of discounts on marketable securities	(580)	36
Deferred income taxes	1,643	140
Changes in operating assets and liabilities:
Accounts receivable	7,962	14,538
Prepaid expenses and other assets	(3,194)	(2,341)
Accounts payable	(1,374)	(302)
Accrued liabilities	316	4,577
Deferred revenues	9,855	2,330
Other non-current liabilities	(32)	(1,072)
Net cash provided by operating activities	44,347	42,989
Cash flows from investing activities:
Purchases of marketable securities	(66,224)	(72,176)
Sales and maturities of marketable securities	91,046	40,080
Purchases of property and equipment	(8,608)	(5,985)
Business combinations	850	0
Net cash provided by (used in) investing activities	15,364	(38,081)
Cash flows from financing activities:
Proceeds from exercise of stock options	4,047	7,933
Payments for taxes related to net share settlement of equity awards	(3,367)	(4,030)
Principal payments under capital lease obligations	(419)	(747)
Repurchase of common stock	(7,871)	(1,481)
Net cash (used in) provided by financing activities	(7,610)	1,675
Net increase in cash, cash equivalents and restricted cash	52,101	6,583
Cash, cash equivalents and restricted cash at beginning of period	42,226	87,791
Cash, cash equivalents and restricted cash at end of period	$ 94,327	$ 94,374

The Company and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
The Company and Summary of Significant Accounting Policies	The Company and Summary of Significant Accounting Policies Description of Business Qualys, Inc. (the “Company”, "we", "us", "our") was incorporated in the state of Delaware on December 30, 1999. The Company is headquartered in Foster City, California and has wholly-owned subsidiaries throughout the world. The Company is a pioneer and leading provider of cloud-based security and compliance solutions that enable organizations to identify security risks to their IT infrastructures, help protect their IT systems and applications from ever-evolving cyber-attacks and achieve compliance with internal policies and external regulations. The Company’s cloud solutions address the growing security and compliance complexities and risks that are amplified by the dissolving boundaries between internal and external IT infrastructures and web environments, the rapid adoption of cloud computing and the proliferation of geographically dispersed IT assets. Organizations can use the Company’s integrated suite of solutions delivered on its Qualys cloud platform to cost-effectively obtain a unified view of their security and compliance posture across globally-distributed IT infrastructures. Basis of Presentation The accompanying unaudited condensed consolidated financial statements and condensed footnotes have been prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP") for interim financial information as well as the instructions to Form 10-Q and the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Certain information and disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. The condensed consolidated balance sheet as of December 31, 2018, included herein, was derived from the audited financial statements as of that date but does not include all disclosures, including notes required by U.S. GAAP. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the financial position, results of operations and cash flows for the interim periods. The results of operations for the three month period ended March 31, 2019 are not necessarily indicative of the results of operations expected for the entire year ending December 31, 2019 or for any other future annual or interim periods. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the SEC on February 27, 2019. Use of Estimates The preparation of the unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of assets and liabilities at the date of the condensed consolidated financial statements and the reported results of operations during the reporting period. The Company’s management regularly assesses these estimates, which primarily affect revenue recognition, the valuation of accounts receivable, goodwill and intangible assets, capitalization of internally developed software, stock-based compensation and the provision for income taxes. Actual results could differ from those estimates and such differences may be material to the accompanying unaudited condensed consolidated financial statements. Derivative Financial Instruments Derivative financial instruments are utilized by the Company to reduce foreign currency exchange risks. The Company uses foreign currency forward contracts to mitigate the impact of foreign currency fluctuations of certain non-U.S. Dollar denominated asset positions, to date primarily cash and accounts receivable (non-designated), as well as to manage foreign currency fluctuation risk related to forecasted transactions (designated). The Company accounts for these instruments as either non-designated or cash flow hedges, respectively. Open contracts are recorded within prepaid expenses and other current assets or accrued liabilities in the consolidated balance sheets. Gains and losses resulting from currency exchange rate movements on non-designated forward contracts are recognized in other income (expense). Any gains or losses from derivatives designated as cash flow hedges are first accumulated in other comprehensive income (AOCI) and then reclassified to revenue when the hedged item impacts the consolidated financial statements. The cash flow effects of the Company's derivative contracts for the three months ended March 31, 2019 were included within net cash provided by operating activities on its condensed consolidated statements of cash flows. The Company had notional amounts on foreign currency exchange contracts designated as cash flow hedges outstanding of €17.7 million and £8.0 million as of March 31, 2019. The unrealized foreign exchange losses on these contracts were recorded in AOCI and are insignificant. The Company has no hedges designated as cash flow hedges in the prior year's quarter ending March 31, 2018. Stock-Based Compensation The Company recognizes the fair value of its employee stock options and restricted stock units (RSUs) over the requisite service period for those awards ultimately expected to vest. The fair value of each option is estimated on date of grant using the Black-Scholes-Merton option pricing model and the fair value of each restricted stock unit is based on the fair value of the Company's stock on the date of grant. Forfeitures are estimated on the date of grant and revised if actual or expected forfeiture activity differs materially from original estimates. Option grants to non-employees are accounted for at the fair value of the equity instrument issued, as calculated using the Black-Scholes-Merton option-pricing model and the expense is recognized over the vesting periods of the options. The value of options granted to non-employees is re-measured as they vest over a performance period. The Company has performance-based awards and accounts for these awards as share-based compensation with multiple performance conditions. The Company assesses these conditions on a quarterly basis and for the three months ended March 31, 2019, the Company recorded approximately $0.3 million of stock-based compensation cost for these awards. For performance-based vesting RSUs, the Company records compensation expense for only the performance milestones that are probable of being achieved, with such expense recorded on a straight-line basis over the expected vesting period. The Company reassesses performance-based estimates each reporting period and, if the estimated service period changes, the Company recognizes all remaining compensation expense over the remaining service period and, if the probability of achievement changes to or from “probable,” the Company recognizes the cumulative effect. Internally Developed Software Costs The Company capitalizes certain costs incurred to develop new internal-use software. Capitalized costs include salaries, benefits, and stock-based compensation charges for employees that are directly involved in developing its cloud security platform during the application development stage. These capitalized costs are included in other noncurrent assets on the accompanying condensed consolidated balance sheets. Such costs are amortized on a straight-line basis over its estimated useful life of three years. Amortization of internally developed software is recorded to cost of revenues. Capitalization of internally developed software cost was $0.2 million for the three months ended March 31, 2019. Unamortized cost for capitalized internally developed software was $1.4 million at March 31, 2019 and $1.2 million at December 31, 2018. Amortization expense for capitalized internally developed software was insignificant for the three months ended March 31, 2019. Management evaluates the useful lives of these assets on an annual basis and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. Cost Method Investments In the second quarter of fiscal 2018, the Company invested $2.5 million in a privately-held company. The Company used the cost method of accounting to account for the investment because the Company does not hold a controlling interest in this entity and does not have the ability to exercise significant influence over the entity's operating and financial policies. The investment is included in long term assets on the accompanying condensed consolidated balance sheets. The Company's cost method investment is assessed for impairment when events or changes in circumstances indicate that the carrying amount may not be recoverable. The Company has not recorded any dividends or other-than-temporary impairment charges related to its cost method investment. The fair value of the investment is not readily available, and there are no quoted market prices for the investment. Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize all leases, including operating leases, on the balance sheet as a lease asset and lease liability, unless the lease is a short-term lease. ASU 2016-02 also requires additional disclosures regarding leasing arrangements. ASU 2016-02 is effective for the Company beginning in the first quarter of fiscal 2019 and early adoption is permitted. In July 2018, the FASB issued ASU 2018-11, Targeted Improvements - Leases (Topic 842). This update provides an optional transition method that allows entities to elect to apply the standard prospectively at its effective date, versus recasting the prior periods presented. If elected, an entity would recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Pursuant to the leasing criteria, most of the Company's leased space and equipment leases will be required to be accounted for as right-of-use assets on the balance sheet with offsetting financing obligations. In the statement of operations, what was formerly rent expense for operating leases will be lease expense; and finance leases will be bifurcated into amortization of right-of-use assets and interest on lease liabilities. The Company adopted the ASU utilizing the current period adjustment method on January 1, 2019, and recognized an ROU asset of $30.8 million and a lease liability of $41.6 million on its condensed consolidated financial statements. As of December 31, 2018, $3.9 million of deferred rent and $6.9 million related to tenant improvement allowance was removed upon adoption. As part of this adoption, the Company elected the package of transitional practical expedients to not reassess (1) whether any contracts that existed prior to adoption have or contain leases, (2) the classification of existing leases or (3) initial direct costs for existing leases. In February 2018, the FASB issued ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (AOCI). This ASU eliminates the stranded tax effects in other comprehensive income resulting from the Tax Cuts and Jobs Act (the "2017 Tax Act”). Because the amendments only relate to the reclassification of the income tax effects of the 2017 Tax Act, the underlying guidance that requires that the effect of a change in tax laws or rates be included in income from continuing operations is not affected. The Company adopted ASU 2018-02 in the fourth quarter of 2018. The adoption of this ASU did not have an impact on the Company's condensed consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. This ASU expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company adopted this guidance during the three months ended March 31, 2019. The adoption of this ASU did not have a material impact on the Company's condensed consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (Topic 350). This standard eliminates Step 2 from the goodwill impairment test, instead requiring an entity to recognize a goodwill impairment charge for the amount by which the goodwill carrying amount exceeds the reporting unit’s fair value. This ASU is effective for interim and annual goodwill impairment tests in fiscal years beginning after December 15, 2019 with early adoption permitted. This ASU must be applied on a prospective basis. The Company has adopted this ASU during the three months ended March 31, 2019 and the adoption did not have a material impact on the Company's condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In August 2018, the FASB issued ASU 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. This ASU aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs related to internal-use software. ASU 2018-15 is effective for the Company beginning in the first quarter of fiscal 2020 and early adoption is permitted. The Company is currently evaluating the impact of this ASU on its condensed consolidated financial statements.

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. For certain of the Company’s financial instruments, including certain cash equivalents, accounts receivable, accounts payable, and other current liabilities, the carrying amounts approximate their fair values due to the relatively short maturity of these balances.

The Company measures and reports certain cash equivalents, marketable securities, derivative foreign currency forward contracts and commitments associated with prior business combinations at fair value in accordance with the provisions of the authoritative accounting guidance that addresses fair value measurements. This guidance establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. The hierarchy is broken down into three levels based on the reliability of inputs as follows:

Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities.

Level 2—Valuations based on other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3—Valuations based on inputs that are generally unobservable and typically reflect management’s estimates of assumptions that market participants would use in pricing the asset or liability.

The Company's financial instruments consist of assets and liabilities measured using Level 1 and 2 inputs. Level 1 assets include a highly liquid money market fund, which is valued using unadjusted quoted prices that are available in an active market for an identical asset. Level 2 assets include fixed-income U.S. government agency securities, commercial paper, corporate bonds, asset-backed securities and derivative financial instruments consisting of foreign currency forward contracts. The securities, bonds and commercial paper are valued using prices from independent pricing services based on quoted prices in active markets for similar instruments or on industry models using data inputs such as interest rates and prices that can be directly observed or corroborated in active markets. The foreign currency forward contracts are valued using observable inputs, such as quotations on forward foreign exchange points and foreign interest rates. The estimated fair value of commitments from prior acquisitions are determined based on management’s estimate of fair value using a Monte Carlo simulation model, which uses Level 3 inputs for fair value measurements. During the quarter ended March 31, 2019, management estimated the fair value of such commitments to be zero.

The Company's cash and cash equivalents, and marketable securities consist of the following:



	March 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Cash and cash equivalents:
Cash	$	93,070	$	—	$	—		$	93,070
Money market funds	57		—		—			57
Total	93,127		—		—			93,127
Short-term marketable securities:
Corporate bonds	38,990		—		(77		)	38,913
Asset-backed securities	9,868		—		—			9,868
U.S. government agencies	156,216		39		(27		)	156,228
Total	205,074		39		(104		)	205,009
Long-term marketable securities:
Asset-backed securities	37,588		79		(4		)	37,663
U.S. government agencies	31,212		139		(19		)	31,332
Corporate bonds	27,279		86		(38		)	27,327
Total	96,079		304		(61		)	96,322
Total	$	394,280	$	343	$	(165	)	$	394,458



	December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Cash and cash equivalents:
Cash	$	40,913	$	—	$	—		$	40,913
Money market funds	113		—		—			113
Total	41,026		—		—			41,026
Short-term marketable securities:
Commercial paper	3,237		—		—			3,237
Corporate bonds	30,906		—		(84		)	30,822
Asset-backed securities	10,447		—		(15		)	10,432
U.S. government agencies	203,734		9		(94		)	203,649
Total	248,324		9		(193		)	248,140
Long-term marketable securities:
Asset-backed securities	22,945		10		(28		)	22,927
U.S. government agencies	18,804		—		(53		)	18,751
Corporate bonds	35,322		3		(293		)	35,032
Total	77,071		13		(374		)	76,710
Total	$	366,421	$	22	$	(567	)	$	365,876

The following table shows the changes to accumulated other comprehensive loss for the three months ended March 31, 2019 (in thousands):



	Unrealized (Loss) Gain, net
Balance at December 31, 2018	$	(545	)
Change in net unrealized loss on available-for-sale marketable securities, net of tax	655
Amounts reclassified for net realized gain included in net income, net of tax	28
Other comprehensive income, net of tax	683
Balance at March 31, 2019	$	138

The following table sets forth by level within the fair value hierarchy the fair value of the Company's available-for-sale marketable securities measured on a recurring basis, excluding cash and money market funds:



	March 31, 2019
	Level 1		Level 2		Level 3		Fair Value
	(in thousands)
U.S. government agencies	—		187,560		—		187,560
Corporate bonds	—		66,240		—		66,240
Asset-backed securities	—		47,531		—		47,531
Total	$	—	$	301,331	$	—	$	301,331



	December 31, 2018
	Level 1		Level 2		Level 3		Fair Value
	(in thousands)
Commercial paper	$	—	$	3,237	$	—	$	3,237
U.S. government agencies	—		222,400		—		222,400
Corporate bonds	—		65,854		—		65,854
Asset-backed securities	—		33,359		—		33,359
Total	$	—	$	324,850	$	—	$	324,850

There were no transfers between Level 1, Level 2 or Level 3 of the fair value hierarchy, as determined at the end of each reporting period.

The following summarizes the fair value of marketable securities classified as available-for-sale by contractual, or effective, maturity:



	March 31, 2019
	Mature within One Year		Mature after One Year through Two Years		Mature over Two Years		Fair Value
	(in thousands)
U.S. government agencies	156,228		16,736		14,596		187,560
Corporate bonds	38,913		24,825		2,502		66,240
Asset-backed securities	29,336		8,439		9,756		47,531
Total	$	224,477	$	50,000	$	26,854	$	301,331

Derivative Financial Instruments

Derivative financial instruments are utilized by the Company to reduce foreign currency exchange risks. The Company uses foreign currency forward contracts to mitigate the impact of foreign currency fluctuations of certain non-U.S. Dollar denominated asset positions, to date primarily cash and accounts receivable (non-designated), as well as to manage foreign currency fluctuation risk related to forecasted transactions (designated).

At March 31, 2019, the Company had eight outstanding forward contracts with notional amounts of €13.0 million and £5.4 million, respectively. These contracts did not meet the criteria to be designated as cash flow hedges and were valued using Level 2 inputs.

At March 31, 2019, the Company had 24 open contracts with notional amounts that were designated as cash flow hedges of €17.7 million and £8.0 million, respectively. The unrealized FX gains on these contracts were recorded in AOCI for $0.2 million, net of tax.

At December 31, 2018, the Company had two outstanding non-designated forward contracts with notional amounts of €16.0 million and £6.3 million, respectively, both with the expiry date of January 31, 2019.

At December 31, 2018, the Company had two outstanding forward contracts with notional amounts of €12.9 million and £4.1 million, respectively. These derivatives met the criteria to be designated as cash flow hedges and were valued using Level 2 inputs. The unrealized foreign currency losses on these contracts were recorded in AOCI and were insignificant.

The following summarizes the gains (losses) recognized in other income (expense), net on the condensed consolidated statement of operations, from forward contracts and other foreign currency transactions:



	Three Months Ended
	March 31,
	2019			2018
	(in thousands)
Net loss from forward contracts	$	(331	)	$	(578	)
Other foreign currency transactions gain	171			810
Total foreign exchange loss, net	$	(160	)	$	232

- 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

3 Months Ended

Mar. 31, 2019

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

Property and equipment, net, which includes assets under finance lease, consists of the following:



	March 31,			December 31,
	2019			2018
	(in thousands)
Computer equipment	$	98,537		$	93,530
Computer software	26,041			26,030
Furniture, fixtures and equipment	5,907			5,814
Finance leases - right of use asset	3,503			3,503
Scanner appliances	15,665			15,356
Leasehold improvements	16,469			16,439
Total property and equipment	166,122			160,672
Less: accumulated depreciation and amortization	(105,636		)	(99,230		)
Property and equipment, net	$	60,486		$	61,442

Physical scanner appliances and other computer equipment have a net carrying value of $7.5 million and $7.9 million at March 31, 2019 and December 31, 2018, respectively, including assets that have not been placed in service of $1.2 million and $1.8 million, respectively. Depreciation and amortization expense relating to property and equipment, including capitalized leases, was $6.4 million and $6.4 million for the three months ended March 31, 2019 and 2018, respectively. Accumulated depreciation under finance leases was $1.3 million at March 31, 2019.

Revenue from Contracts with Customers

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Revenue from Contracts with Customers

The Company's performance obligation is typically satisfied ratably over the subscription term as its cloud-based offerings are delivered to customers electronically and over time. In addition, the Company recognizes revenues for certain limited scan arrangements on an as-used basis. The Company recognizes revenue related to the professional services based on time and materials or completion of milestones stated in the contracts.

As the vast majority of the Company’s offerings are subscription based, the Company rarely needs to allocate the transaction price to all separate performance obligations. For contracts that include scanners and PCPs, the Company recognizes revenue in proportion to the standalone selling prices ("SSP") of the underlying services at contract inception. If an SSP is not directly observable, the Company determines the SSP using information that may include market conditions and other observable inputs. The Company's transaction prices typically do not include variable consideration and are a fixed amount for a specific period of time, and the majority of contracts are twelve months with certain customers signing longer term deals. In general, the Company does not offer rights of return, performance bonuses, customer loyalty programs, payments via non-cash methods, refunds, volume rebates, incentive payments, penalties, price concessions or payments or discounts contingent on future events and the Company does not grant its customers any material rights.

Costs of shipping and handling charges associated with physical scanner appliances and other computer equipment are included in cost of revenues. Sales taxes and other taxes collected from customers to be remitted to government authorities are excluded from revenues.

Incremental direct costs of obtaining a contract, which consist of sales commissions primarily for new business and upsells, are deferred and amortized over the estimated life of the customer relationship if renewals are expected and the renewal commission is not commensurate with the initial commission. The Company amortizes the capitalized commission cost as a selling expense on a straight-line basis over a period of five years. The Company classifies deferred commissions as current or noncurrent based on the timing of when it expects to recognize the expense. The current and noncurrent portions of deferred commissions are included in prepaid expenses and other current assets and other noncurrent assets, respectively, in its condensed consolidated balance sheets.

Commission asset balances are as follows (in thousands):



	March 31, 2019		December 31, 2018
Commission asset, current	$	1,691	$	1,480
Commission asset, noncurrent	$	5,087	$	4,692

For the three months ended March 31, 2019 and 2018, the Company recognized $0.4 million and $0.2 million, respectively, of commission expense from amortization of its commission assets. During the same periods, there was no impairment loss related to capitalized costs.

The Company records deferred revenue when cash payments are received or due in advance of its performance offset by revenue recognized in the period. $64.2 million and $55.6 million of revenue was recognized during the three months ended March 31, 2019 and 2018, respectively, which amounts were included in the unearned revenue balances as of December 31, 2018 and 2017, respectively.

Accounts receivable, net, consists of the following (in thousands):



	March 31, 2019			December 31, 2018
Accounts receivable	$	68,516		$	76,508
Less: allowance for doubtful accounts	(653		)	(683		)
Total accounts receivable, net	$	67,863		$	75,825

The Company's payment terms vary by the type and location of its customer and the products or services offered. The term between invoicing and when payment is due is not significant. For certain products or services and customer types, the Company requires payment before the products or services are delivered to the customer.

The following table sets forth the expected revenue from all remaining performance obligations as of March 31, 2019 (in thousands):



	Total Expected Revenue
2019 (nine months remaining)	$	46,413
2020	35,226
2021	15,727
2022	2,098
2023	902
2024 and thereafter	123
Total	$	100,489

Business Combination Business Combination	3 Months Ended
Business Combination Business Combination	Mar. 31, 2019
Business Combinations [Abstract]
Business Combination	Business Combination On January 10, 2019, the Company acquired the assets of Adya, Inc. ("Adya"), an India-based company. The acquisition included a cloud application management platform, which enables security and compliance audits of SaaS applications. Total purchase consideration was $1.0 million, including $0.2 million of deferred consideration due eighteen months from the closing date of the acquisition, subject to potential adjustment from possible indemnity claims. Pro forma financial information for this acquisition has not been presented because it is not material to the Company's condensed consolidated financial statements. The Company accounted for this transaction as a business combination and allocated $0.9 million of the purchase price to technology-based intangible assets and $0.1 million to goodwill. The acquired intangible assets relating to Adya's developed technology are being amortized over the estimated useful lives of approximately four years. Goodwill arising from the Adya acquisition is deductible for tax purposes over 15 years.

Goodwill and Intangible Assets, Net

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets, Net

will and Intangible Assets, Net

Intangible assets consist primarily of developed technology and patent licenses from business combinations. Acquired intangibles are amortized on a straight-line basis over the respective estimated useful lives of the assets.

The carrying values of intangible assets are as follows (in thousands, except for years):



					March 31, 2019
	Weighted Average Life (Years)	Weighted Average Remaining Life (Years)	Cost		Accumulated Amortization			Net Book Value
Developed technology	5 years	3.5	$	26,356	$	(5,580	)	$	20,776
Patent licenses	14 years	5.4	1,387		(847		)	540
Total intangibles subject to amortization			$	27,743	$	(6,427	)	21,316
Intangible assets not subject to amortization								40
Total intangible assets, net								$	21,356

					December 31, 2018
	Weighted Average Life (Years)	Weighted Average Remaining Life (Years)	Cost		Accumulated Amortization			Net Book Value
Developed technology	5 years	3.8	$	25,456	$	(4,085	)	$	21,371
Patent Licenses	14 years	5.9	1,387		(822		)	565
Total intangibles subject to amortization			$	26,843	$	(4,907	)	21,936
Intangible assets not subject to amortization								40
Total intangible assets, net								$	21,976

Intangible asset amortization expense was $1.5 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively.

As of March 31, 2019, the Company expects amortization expense in future periods to be as follows (in thousands):



2019 (remaining nine months)	$	4,561
2020	6,081
2021	6,081
2022	4,427
2023	100
2024 and thereafter	66
Total expected future amortization expense	$	21,316

Goodwill, which is not subject to amortization, totaled $7.3 million and $7.2 million as of March 31, 2019 and December 31, 2018, respectively.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Leases (Notes)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Leases

On January 1, 2019, the Company adopted ASU No. 2016-02, “Leases (Topic 842),” which requires leases with durations greater than twelve months to be recognized on the balance sheet. We adopted the standard using the current period adjustment method with an effective date of January 1, 2019. Prior year financial statements were not restated under the new standard and, therefore, those amounts are not presented below. For both operating and finance leases, we recognize a right-of-use asset, which represents our right to use the underlying asset for the lease term, and a lease liability, which represents the present value of our obligation to make payments arising over the lease term. The present value of the lease payments is calculated using the incremental borrowing rate for operating and finance leases. The incremental borrowing rate is determined using a portfolio approach based on the rate of interest that the Company would have to pay to borrow an amount equal to the lease payments on a collateralized basis over a similar term.

Where the Company is the lessee, we have elected to account for non-lease components associated with our leases (e.g., common area maintenance costs) and lease components separately for substantially all of our asset classes. In arrangements where we are the lessor, we have customer premise equipment for which we apply the lease and non-lease component practical expedient and account for non-lease component practical expedient and account for non-lease components (e.g., service revenue) and lease components as combined components under the revenue recognition guidance in ASU 2014-09, "Revenue from Contracts with Customers" (Topic 606) as the service revenues are the predominant components in the arrangements.

We lease property and equipment under finance and operating leases. For leases with terms greater than 12 months, we record the related asset and obligation at the present value of lease payments over the term. Many of our leases include rental escalation clauses, renewal options and/or termination options that are factored into our determination of lease payments when appropriate.

When available, we use the rate implicit in the lease to discount lease payments to present value; however, most of our leases do not provide a readily determinable implicit rate. Therefore, we must estimate our incremental borrowing rate to discount the lease payments based on information available at lease commencement.

The table below presents the lease-related assets and liabilities recorded on the balance sheet.



		March 31,
(in thousands)	Classification on the Balance Sheet	2019
Assets
Operating lease assets	Operating lease - right of use asset	$	29,604
Finance lease assets	Property and equipment, net	2,175
Total lease assets		$	31,779

Liabilities
Current
Operating	Accrued liabilities	$	6,760
Finance	Finance lease, current	1,153
Noncurrent
Operating	Operating lease liability, noncurrent	33,589
Finance	Other noncurrent liabilities	148
Total lease liabilities		$	41,650

The Company leases certain computer equipment and its corporate office and data center facilities under non-cancelable operating leases for varying periods through 2028. In January 2018, the Company entered into a $3.5 million financing arrangement for data center storage equipment, accounted for as a finance lease, with an implied interest rate of 5%.

The following are the minimum annual lease payments due under these leases at March 31, 2019 (in thousands):



	Operating Leases			Finance Leases
	(in thousands)
2019 (remaining nine months)	$	6,601		$	1,328
2020	7,819			130
2021	6,124			54
2022	4,542			—
2023	4,298			—
2024 and thereafter	19,299			—
Total minimum lease payments	48,683			1,512
Less: amount representing interest	(8,334		)	(211		)
Present value of minimum payments	40,349			1,301
Less: current portion	(6,760		)	(1,153		)
Lease obligations, noncurrent	$	33,589		$	148

Lease expense was $1.6 million and $2.2 million for the three months ended March 31, 2019 and 2018, respectively.

The weighted average remaining lease term and the weighted average discount rate of our leases were as follows:



	March 31, 2019
Weighted average remaining lease term (years)
Operating leases	8
Finance leases	2
Weighted average discount rates
Operating leases	4.5	%
Finance leases	5.0	%

Leases

The table below presents the lease-related assets and liabilities recorded on the balance sheet.



		March 31,
(in thousands)	Classification on the Balance Sheet	2019
Assets
Operating lease assets	Operating lease - right of use asset	$	29,604
Finance lease assets	Property and equipment, net	2,175
Total lease assets		$	31,779

Liabilities
Current
Operating	Accrued liabilities	$	6,760
Finance	Finance lease, current	1,153
Noncurrent
Operating	Operating lease liability, noncurrent	33,589
Finance	Other noncurrent liabilities	148
Total lease liabilities		$	41,650

The following are the minimum annual lease payments due under these leases at March 31, 2019 (in thousands):



	Operating Leases			Finance Leases
	(in thousands)
2019 (remaining nine months)	$	6,601		$	1,328
2020	7,819			130
2021	6,124			54
2022	4,542			—
2023	4,298			—
2024 and thereafter	19,299			—
Total minimum lease payments	48,683			1,512
Less: amount representing interest	(8,334		)	(211		)
Present value of minimum payments	40,349			1,301
Less: current portion	(6,760		)	(1,153		)
Lease obligations, noncurrent	$	33,589		$	148

Lease expense was $1.6 million and $2.2 million for the three months ended March 31, 2019 and 2018, respectively.

The weighted average remaining lease term and the weighted average discount rate of our leases were as follows:



	March 31, 2019
Weighted average remaining lease term (years)
Operating leases	8
Finance leases	2
Weighted average discount rates
Operating leases	4.5	%
Finance leases	5.0	%

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Indemnifications The Company from time to time enters into certain types of contracts that contingently require it to indemnify various parties against claims from third parties. These contracts primarily relate to (i) the Company's by-laws, under which it must indemnify directors and executive officers, and may indemnify other officers and employees, for liabilities arising out of their relationship, (ii) contracts under which the Company must indemnify directors and certain officers for liabilities arising out of their relationship, and (iii) contracts under which the Company may be required to indemnify customers or resellers from certain liabilities arising from potential infringement of intellectual property rights, as well as potential damages caused by limited product defects. To date, the Company has not incurred and has not recorded any liability in connection with such indemnifications. The Company maintains director and officer insurance, which may cover certain liabilities arising from its obligation to indemnify its directors.

Stock-based Compensation

3 Months Ended

Mar. 31, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based Compensation

Equity Incentive Plans

2012 Equity Incentive Plan

Under the 2012 Equity Incentive Plan (the "2012 Plan"), the Company is authorized to grant to eligible participants incentive stock options (“ISOs”), non-statutory stock options (“NSOs”), stock appreciation rights ("SARs"), restricted stock awards ("RSAs"), restricted stock units ("RSUs"), performance units and performance shares equivalent to up to 11,791,179 shares of common stock as of March 31, 2019. Options may be granted with an exercise price that is at least equal to the fair market value of the Company's stock at the date of grant and are exercisable when vested. As of March 31, 2019, 3,827,360 shares were available for grant under the 2012 Plan.

2000 Equity Incentive Plan

Under the 2000 Equity Incentive Plan (the "2000 Plan"), the Company was authorized to grant to eligible participants either ISOs or NSOs. The 2000 Plan was terminated in connection with the closing of the Company's initial public offering, and accordingly, no shares are currently available for grant under the 2000 Plan. The 2000 Plan continues to govern outstanding awards granted thereunder.

Stock-based Compensation

The following table shows a summary of the stock-based compensation expense included in the condensed consolidated statements of operations for the three months ended March 31, 2019 and 2018:



	Three Months Ended
	March 31,
	2019		2018
	(in thousands)
Cost of revenues	$	545	$	654
Research and development	2,340		1,841
Sales and marketing	1,068		1,401
General and administrative	4,492		4,995
Total stock-based compensation	$	8,445	$	8,891

As of March 31, 2019, the Company had $13.9 million of total unrecognized stock-based compensation cost related to unvested options that it expects to recognize over a weighted-average period of 2.1 years, and $52.6 million of unrecognized stock-based compensation cost related to unvested awards that it expects to recognize over a weighted-average period of 2.6 years. Compensation cost is recognized on a straight-line basis over the service period. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

Stock Option Plan Activity

A summary of the Company’s stock option activity is as follows:



	Outstanding Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
						(in thousands)
Balance as of December 31, 2018	3,429,309		$	31.79	6.4	$	149,935
Granted	103,275		$	94.45
Exercised	(152,164	)	$	26.59
Canceled	(33,355	)	$	50.49
Balance as of March 31, 2019	3,347,065		$	33.77	6.3	$	166,381
Vested and expected to vest - March 31, 2019	3,160,808		$	31.89	6.1	$	162,480
Exercisable - March 31, 2019	2,446,532		$	25.76	5.6	$	139,401

Restricted Stock

A summary of the Company’s RSU activity is as follows:



	Outstanding RSUs		Weighted Average Grant Date Fair Value Per Share

Balance as of December 31, 2018	1,226,883		$	55.71
Granted	124,857		$	79.69
Vested	(99,601	)	$	47.71
Canceled	(53,272	)	$	56.56
Balance as of March 31, 2019	1,198,867		$	58.83
Outstanding and expected to vest - March 31, 2019	883,174		$	57.74

Net Income Per Share

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Net Income Per Share

The computations for basic and diluted net income per share are as follows:



	Three Months Ended
	March 31,
	2019		2018
	(in thousands, except per share data)
Numerator:
Net income	$	13,266	$	9,142
Denominator:
Weighted-average shares used in computing net income per share:
Basic	39,109		38,789
Effect of potentially dilutive securities:
Common stock options	1,970		2,503
Restricted stock units	467		642
Diluted	41,546		41,934
Net income per share:
Basic	$	0.34	$	0.24
Diluted	$	0.32	$	0.22

Potentially dilutive securities not included in the calculation of diluted net income per share because doing so would be antidilutive are as follows:



	Three Months Ended
	March 31,
	2019	2018
	(in thousands)
Common stock options	343	109
Restricted stock units	38	—
	381	109

Stockholder's Equity	3 Months Ended
Stockholder's Equity	Mar. 31, 2019
Equity [Abstract]
Stockholder's Equity	Stockholder's Equity Share Repurchase Program On February 5, 2018, the Company's board of directors authorized a $100.0 million share repurchase program, which was announced on February 12, 2018. On October 30, 2018, the Company announced that the board of directors had authorized an increase of $100.0 million to the original share repurchase program authorization. Share repurchases may be effected from time to time through open market purchases or pursuant to a Rule 10b5-1 plan until October 30, 2020. Repurchased shares are retired and reclassified as authorized and unissued shares of common stock. On retirement of the repurchased shares, common stock is reduced by an amount equal to the number of shares being retired multiplied by the par value. The excess of the cost of treasury stock that is retired over its par value is first allocated as a reduction to additional paid-in capital based on the initial public offering price of the stock, with the remaining excess to retained earnings. During the three months ended March 31, 2019, the Company repurchased 94,090 shares of its common stock for approximately $7.9 million. During the three months ended March 31, 2018, the Company repurchased 21,288 shares of its common stock for approximately $1.5 million. All share repurchases were made using cash resources. As of March 31, 2019, approximately $107.1 million remained available for share repurchases pursuant to the share repurchase program.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company's provision for income taxes for interim periods is determined using an estimate of its annual effective tax rate, adjusted for discrete items, if any, that arise during the period. Each quarter, the Company updates its estimate of the annual effective tax rate, and if the estimated annual effective tax rate changes, the Company makes a cumulative adjustment in such period. The Company's quarterly tax provision, and estimate of its annual effective tax rate, is subject to variation due to several factors, including variability in pre-tax income (or loss), the mix of jurisdictions to which such income relates, changes in how the Company does business, and tax law developments. The Company's estimated effective tax rate for the year differs from the U.S. statutory rate of 21% primarily due to non-deductible stock-based compensation expense, state taxes, foreign income subject to different tax rates than the U.S., and the benefit of U.S. federal income tax credits. The Company recorded an income tax provision of $2.6 million and income tax provision of $0.5 million for the three months ended March 31, 2019 and 2018, respectively, resulting in an effective tax rate of 16.2% and 5.3%, respectively. The tax provision for the three months ended March 31, 2019 as compared to the tax provision for the three months ended March 31, 2018 changed primarily due to an increase in pre-tax income and decrease in the tax benefit of excess stock-based compensation deductions. As of March 31, 2019, the Company had unrecognized tax benefits of $6.9 million, of which $3.8 million, if recognized, would favorably impact the Company's effective tax rate. As of December 31, 2018, the Company had unrecognized tax benefits of $6.4 million, of which $3.5 million, if recognized, would favorably impact the Company's effective tax rate. The Company does not anticipate a material change in its unrecognized tax benefits in the next 12 months.

Segment Information and Information about Geographic Area

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Segment Information and Information about Geographic Area

he Company operates in one segment. The Company determines its reportable operating segments in accordance with the provisions in the FASB guidance on segment reporting, which establishes standards for, and requires disclosure of, certain financial information related to reportable operating segments and geographic regions. The Company’s chief operating decision maker is the Chairman, President and Chief Executive Officer, who makes operating decisions, assesses performance and allocates resources on a consolidated basis. All of the Company’s principal operations and decision-making functions are located in the United States.

Revenues by geographic area, based on the location of the customer, are as follows (in thousands):



	Three Month Ended March 31,
	2019		2018
United States	$	48,621	$	44,314
Foreign	26,722		20,564
Total	$	75,343	$	64,878

Property and equipment, net, by geographic area, are as follows:



	March 31,		December 31,
	2019		2018
	(in thousands)
United States	$	57,810	$	59,222
Foreign	2,676		2,220
Total property and equipment, net	$	60,486	$	61,442

The Company and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Description Of Business	Description of Business Qualys, Inc. (the “Company”, "we", "us", "our") was incorporated in the state of Delaware on December 30, 1999. The Company is headquartered in Foster City, California and has wholly-owned subsidiaries throughout the world. The Company is a pioneer and leading provider of cloud-based security and compliance solutions that enable organizations to identify security risks to their IT infrastructures, help protect their IT systems and applications from ever-evolving cyber-attacks and achieve compliance with internal policies and external regulations. The Company’s cloud solutions address the growing security and compliance complexities and risks that are amplified by the dissolving boundaries between internal and external IT infrastructures and web environments, the rapid adoption of cloud computing and the proliferation of geographically dispersed IT assets. Organizations can use the Company’s integrated suite of solutions delivered on its Qualys cloud platform to cost-effectively obtain a unified view of their security and compliance posture across globally-distributed IT infrastructures.
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements and condensed footnotes have been prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP") for interim financial information as well as the instructions to Form 10-Q and the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Certain information and disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. The condensed consolidated balance sheet as of December 31, 2018, included herein, was derived from the audited financial statements as of that date but does not include all disclosures, including notes required by U.S. GAAP. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the financial position, results of operations and cash flows for the interim periods. The results of operations for the three month period ended March 31, 2019 are not necessarily indicative of the results of operations expected for the entire year ending December 31, 2019 or for any other future annual or interim periods. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the SEC on February 27, 2019. Use of Estimates The preparation of the unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of assets and liabilities at the date of the condensed consolidated financial statements and the reported results of operations during the reporting period. The Company’s management regularly assesses these estimates, which primarily affect revenue recognition, the valuation of accounts receivable, goodwill and intangible assets, capitalization of internally developed software, stock-based compensation and the provision for income taxes. Actual results could differ from those estimates and such differences may be material to the accompanying unaudited condensed consolidated financial statements. Derivative Financial Instruments Derivative financial instruments are utilized by the Company to reduce foreign currency exchange risks. The Company uses foreign currency forward contracts to mitigate the impact of foreign currency fluctuations of certain non-U.S. Dollar denominated asset positions, to date primarily cash and accounts receivable (non-designated), as well as to manage foreign currency fluctuation risk related to forecasted transactions (designated). The Company accounts for these instruments as either non-designated or cash flow hedges, respectively. Open contracts are recorded within prepaid expenses and other current assets or accrued liabilities in the consolidated balance sheets. Gains and losses resulting from currency exchange rate movements on non-designated forward contracts are recognized in other income (expense). Any gains or losses from derivatives designated as cash flow hedges are first accumulated in other comprehensive income (AOCI) and then reclassified to revenue when the hedged item impacts the consolidated financial statements. The cash flow effects of the Company's derivative contracts for the three months ended March 31, 2019 were included within net cash provided by operating activities on its condensed consolidated statements of cash flows. The Company had notional amounts on foreign currency exchange contracts designated as cash flow hedges outstanding of €17.7 million and £8.0 million as of March 31, 2019. The unrealized foreign exchange losses on these contracts were recorded in AOCI and are insignificant. The Company has no hedges designated as cash flow hedges in the prior year's quarter ending March 31, 2018. Stock-Based Compensation The Company recognizes the fair value of its employee stock options and restricted stock units (RSUs) over the requisite service period for those awards ultimately expected to vest. The fair value of each option is estimated on date of grant using the Black-Scholes-Merton option pricing model and the fair value of each restricted stock unit is based on the fair value of the Company's stock on the date of grant. Forfeitures are estimated on the date of grant and revised if actual or expected forfeiture activity differs materially from original estimates. Option grants to non-employees are accounted for at the fair value of the equity instrument issued, as calculated using the Black-Scholes-Merton option-pricing model and the expense is recognized over the vesting periods of the options. The value of options granted to non-employees is re-measured as they vest over a performance period. The Company has performance-based awards and accounts for these awards as share-based compensation with multiple performance conditions. The Company assesses these conditions on a quarterly basis and for the three months ended March 31, 2019, the Company recorded approximately $0.3 million of stock-based compensation cost for these awards. For performance-based vesting RSUs, the Company records compensation expense for only the performance milestones that are probable of being achieved, with such expense recorded on a straight-line basis over the expected vesting period. The Company reassesses performance-based estimates each reporting period and, if the estimated service period changes, the Company recognizes all remaining compensation expense over the remaining service period and, if the probability of achievement changes to or from “probable,” the Company recognizes the cumulative effect. Internally Developed Software Costs The Company capitalizes certain costs incurred to develop new internal-use software. Capitalized costs include salaries, benefits, and stock-based compensation charges for employees that are directly involved in developing its cloud security platform during the application development stage. These capitalized costs are included in other noncurrent assets on the accompanying condensed consolidated balance sheets. Such costs are amortized on a straight-line basis over its estimated useful life of three years. Amortization of internally developed software is recorded to cost of revenues. Capitalization of internally developed software cost was $0.2 million for the three months ended March 31, 2019. Unamortized cost for capitalized internally developed software was $1.4 million at March 31, 2019 and $1.2 million at December 31, 2018. Amortization expense for capitalized internally developed software was insignificant for the three months ended March 31, 2019. Management evaluates the useful lives of these assets on an annual basis and tests for impairment whenever events or changes in circumstances occur that could impact the recoverability of these assets. Cost Method Investments In the second quarter of fiscal 2018, the Company invested $2.5 million in a privately-held company. The Company used the cost method of accounting to account for the investment because the Company does not hold a controlling interest in this entity and does not have the ability to exercise significant influence over the entity's operating and financial policies. The investment is included in long term assets on the accompanying condensed consolidated balance sheets. The Company's cost method investment is assessed for impairment when events or changes in circumstances indicate that the carrying amount may not be recoverable. The Company has not recorded any dividends or other-than-temporary impairment charges related to its cost method investment. The fair value of the investment is not readily available, and there are no quoted market prices for the investment. Recently Adopted Accounting Pronouncements
Recently adopted Accounting Pronouncements and Recent Accounting Pronouncements	In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize all leases, including operating leases, on the balance sheet as a lease asset and lease liability, unless the lease is a short-term lease. ASU 2016-02 also requires additional disclosures regarding leasing arrangements. ASU 2016-02 is effective for the Company beginning in the first quarter of fiscal 2019 and early adoption is permitted. In July 2018, the FASB issued ASU 2018-11, Targeted Improvements - Leases (Topic 842). This update provides an optional transition method that allows entities to elect to apply the standard prospectively at its effective date, versus recasting the prior periods presented. If elected, an entity would recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Pursuant to the leasing criteria, most of the Company's leased space and equipment leases will be required to be accounted for as right-of-use assets on the balance sheet with offsetting financing obligations. In the statement of operations, what was formerly rent expense for operating leases will be lease expense; and finance leases will be bifurcated into amortization of right-of-use assets and interest on lease liabilities. The Company adopted the ASU utilizing the current period adjustment method on January 1, 2019, and recognized an ROU asset of $30.8 million and a lease liability of $41.6 million on its condensed consolidated financial statements. As of December 31, 2018, $3.9 million of deferred rent and $6.9 million related to tenant improvement allowance was removed upon adoption. As part of this adoption, the Company elected the package of transitional practical expedients to not reassess (1) whether any contracts that existed prior to adoption have or contain leases, (2) the classification of existing leases or (3) initial direct costs for existing leases. In February 2018, the FASB issued ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (AOCI). This ASU eliminates the stranded tax effects in other comprehensive income resulting from the Tax Cuts and Jobs Act (the "2017 Tax Act”). Because the amendments only relate to the reclassification of the income tax effects of the 2017 Tax Act, the underlying guidance that requires that the effect of a change in tax laws or rates be included in income from continuing operations is not affected. The Company adopted ASU 2018-02 in the fourth quarter of 2018. The adoption of this ASU did not have an impact on the Company's condensed consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. This ASU expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company adopted this guidance during the three months ended March 31, 2019. The adoption of this ASU did not have a material impact on the Company's condensed consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (Topic 350). This standard eliminates Step 2 from the goodwill impairment test, instead requiring an entity to recognize a goodwill impairment charge for the amount by which the goodwill carrying amount exceeds the reporting unit’s fair value. This ASU is effective for interim and annual goodwill impairment tests in fiscal years beginning after December 15, 2019 with early adoption permitted. This ASU must be applied on a prospective basis. The Company has adopted this ASU during the three months ended March 31, 2019 and the adoption did not have a material impact on the Company's condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. For certain of the Company’s financial instruments, including certain cash equivalents, accounts receivable, accounts payable, and other current liabilities, the carrying amounts approximate their fair values due to the relatively short maturity of these balances. The Company measures and reports certain cash equivalents, marketable securities, derivative foreign currency forward contracts and commitments associated with prior business combinations at fair value in accordance with the provisions of the authoritative accounting guidance that addresses fair value measurements. This guidance establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. The hierarchy is broken down into three levels based on the reliability of inputs as follows: Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities. Level 2—Valuations based on other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Valuations based on inputs that are generally unobservable and typically reflect management’s estimates of assumptions that market participants would use in pricing the asset or liability. The Company's financial instruments consist of assets and liabilities measured using Level 1 and 2 inputs. Level 1 assets include a highly liquid money market fund, which is valued using unadjusted quoted prices that are available in an active market for an identical asset. Level 2 assets include fixed-income U.S. government agency securities, commercial paper, corporate bonds, asset-backed securities and derivative financial instruments consisting of foreign currency forward contracts. The securities, bonds and commercial paper are valued using prices from independent pricing services based on quoted prices in active markets for similar instruments or on industry models using data inputs such as interest rates and prices that can be directly observed or corroborated in active markets. The foreign currency forward contracts are valued using observable inputs, such as quotations on forward foreign exchange points and foreign interest rates. The estimated fair value of commitments from prior acquisitions are determined based on management’s estimate of fair value using a Monte Carlo simulation model, which uses Level 3 inputs for fair value measurements. During the quarter ended March 31, 2019, management estimated the fair value of such commitments to be zero.

Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Cash and Cash Equivalents, Available-for-sale Securities Reconciliation

The Company's cash and cash equivalents, and marketable securities consist of the following:



	March 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Cash and cash equivalents:
Cash	$	93,070	$	—	$	—		$	93,070
Money market funds	57		—		—			57
Total	93,127		—		—			93,127
Short-term marketable securities:
Corporate bonds	38,990		—		(77		)	38,913
Asset-backed securities	9,868		—		—			9,868
U.S. government agencies	156,216		39		(27		)	156,228
Total	205,074		39		(104		)	205,009
Long-term marketable securities:
Asset-backed securities	37,588		79		(4		)	37,663
U.S. government agencies	31,212		139		(19		)	31,332
Corporate bonds	27,279		86		(38		)	27,327
Total	96,079		304		(61		)	96,322
Total	$	394,280	$	343	$	(165	)	$	394,458



	December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Cash and cash equivalents:
Cash	$	40,913	$	—	$	—		$	40,913
Money market funds	113		—		—			113
Total	41,026		—		—			41,026
Short-term marketable securities:
Commercial paper	3,237		—		—			3,237
Corporate bonds	30,906		—		(84		)	30,822
Asset-backed securities	10,447		—		(15		)	10,432
U.S. government agencies	203,734		9		(94		)	203,649
Total	248,324		9		(193		)	248,140
Long-term marketable securities:
Asset-backed securities	22,945		10		(28		)	22,927
U.S. government agencies	18,804		—		(53		)	18,751
Corporate bonds	35,322		3		(293		)	35,032
Total	77,071		13		(374		)	76,710
Total	$	366,421	$	22	$	(567	)	$	365,876

Schedule of changes to accumulated other comprehensive income

The following table shows the changes to accumulated other comprehensive loss for the three months ended March 31, 2019 (in thousands):



	Unrealized (Loss) Gain, net
Balance at December 31, 2018	$	(545	)
Change in net unrealized loss on available-for-sale marketable securities, net of tax	655
Amounts reclassified for net realized gain included in net income, net of tax	28
Other comprehensive income, net of tax	683
Balance at March 31, 2019	$	138

Schedule of Assets Measured on Recurring Basis



	March 31, 2019
	Level 1		Level 2		Level 3		Fair Value
	(in thousands)
U.S. government agencies	—		187,560		—		187,560
Corporate bonds	—		66,240		—		66,240
Asset-backed securities	—		47,531		—		47,531
Total	$	—	$	301,331	$	—	$	301,331



	December 31, 2018
	Level 1		Level 2		Level 3		Fair Value
	(in thousands)
Commercial paper	$	—	$	3,237	$	—	$	3,237
U.S. government agencies	—		222,400		—		222,400
Corporate bonds	—		65,854		—		65,854
Asset-backed securities	—		33,359		—		33,359
Total	$	—	$	324,850	$	—	$	324,850

Schedule of Available-for-Sale Securities by Contractual Maturity

The following summarizes the fair value of marketable securities classified as available-for-sale by contractual, or effective, maturity:



	March 31, 2019
	Mature within One Year		Mature after One Year through Two Years		Mature over Two Years		Fair Value
	(in thousands)
U.S. government agencies	156,228		16,736		14,596		187,560
Corporate bonds	38,913		24,825		2,502		66,240
Asset-backed securities	29,336		8,439		9,756		47,531
Total	$	224,477	$	50,000	$	26,854	$	301,331

Summary of Gains (Losses) Recognized From Forward Contracts and Other Foreign Currency Transactions



	Three Months Ended
	March 31,
	2019			2018
	(in thousands)
Net loss from forward contracts	$	(331	)	$	(578	)
Other foreign currency transactions gain	171			810
Total foreign exchange loss, net	$	(160	)	$	232

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Property and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2019

Property, Plant and Equipment [Abstract]

Property and equipment, net

Property and equipment, net, which includes assets under finance lease, consists of the following:



	March 31,			December 31,
	2019			2018
	(in thousands)
Computer equipment	$	98,537		$	93,530
Computer software	26,041			26,030
Furniture, fixtures and equipment	5,907			5,814
Finance leases - right of use asset	3,503			3,503
Scanner appliances	15,665			15,356
Leasehold improvements	16,469			16,439
Total property and equipment	166,122			160,672
Less: accumulated depreciation and amortization	(105,636		)	(99,230		)
Property and equipment, net	$	60,486		$	61,442

Revenue from Contracts with Customers (Tables)

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Commission asset balances

Commission asset balances are as follows (in thousands):



	March 31, 2019		December 31, 2018
Commission asset, current	$	1,691	$	1,480
Commission asset, noncurrent	$	5,087	$	4,692

Contract liabilities

Accounts receivable, net

Accounts receivable, net, consists of the following (in thousands):



	March 31, 2019			December 31, 2018
Accounts receivable	$	68,516		$	76,508
Less: allowance for doubtful accounts	(653		)	(683		)
Total accounts receivable, net	$	67,863		$	75,825

Expected revenue from contracts

The following table sets forth the expected revenue from all remaining performance obligations as of March 31, 2019 (in thousands):



	Total Expected Revenue
2019 (nine months remaining)	$	46,413
2020	35,226
2021	15,727
2022	2,098
2023	902
2024 and thereafter	123
Total	$	100,489

Revenue by sales channel

Revenues by sales channel are as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Direct	$	43,039	$	38,710
Partner	32,304		26,168
Total	$	75,343	$	64,878

Goodwill and Intangible Assets, Net (Tables)

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Carrying value of intangible assets

The carrying values of intangible assets are as follows (in thousands, except for years):



					March 31, 2019
	Weighted Average Life (Years)	Weighted Average Remaining Life (Years)	Cost		Accumulated Amortization			Net Book Value
Developed technology	5 years	3.5	$	26,356	$	(5,580	)	$	20,776
Patent licenses	14 years	5.4	1,387		(847		)	540
Total intangibles subject to amortization			$	27,743	$	(6,427	)	21,316
Intangible assets not subject to amortization								40
Total intangible assets, net								$	21,356

					December 31, 2018
	Weighted Average Life (Years)	Weighted Average Remaining Life (Years)	Cost		Accumulated Amortization			Net Book Value
Developed technology	5 years	3.8	$	25,456	$	(4,085	)	$	21,371
Patent Licenses	14 years	5.9	1,387		(822		)	565
Total intangibles subject to amortization			$	26,843	$	(4,907	)	21,936
Intangible assets not subject to amortization								40
Total intangible assets, net								$	21,976

Intangible assets future periods amortization expense

As of March 31, 2019, the Company expects amortization expense in future periods to be as follows (in thousands

Leases (Tables)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Assets And Liabilities, Lease [Table Text Block]

The table below presents the lease-related assets and liabilities recorded on the balance sheet.



		March 31,
(in thousands)	Classification on the Balance Sheet	2019
Assets
Operating lease assets	Operating lease - right of use asset	$	29,604
Finance lease assets	Property and equipment, net	2,175
Total lease assets		$	31,779

Liabilities
Current
Operating	Accrued liabilities	$	6,760
Finance	Finance lease, current	1,153
Noncurrent
Operating	Operating lease liability, noncurrent	33,589
Finance	Other noncurrent liabilities	148
Total lease liabilities		$	41,650

Lessee, Operating Lease, Liability, Maturity [Table Text Block]

The following are the minimum annual lease payments due under these leases at March 31, 2019 (in thousands):



	Operating Leases			Finance Leases
	(in thousands)
2019 (remaining nine months)	$	6,601		$	1,328
2020	7,819			130
2021	6,124			54
2022	4,542			—
2023	4,298			—
2024 and thereafter	19,299			—
Total minimum lease payments	48,683			1,512
Less: amount representing interest	(8,334		)	(211		)
Present value of minimum payments	40,349			1,301
Less: current portion	(6,760		)	(1,153		)
Lease obligations, noncurrent	$	33,589		$	148

The following are the minimum annual lease payments due under these leases at March 31, 2019 (in thousands):



	Operating Leases			Finance Leases
	(in thousands)
2019 (remaining nine months)	$	6,601		$	1,328
2020	7,819			130
2021	6,124			54
2022	4,542			—
2023	4,298			—
2024 and thereafter	19,299			—
Total minimum lease payments	48,683			1,512
Less: amount representing interest	(8,334		)	(211		)
Present value of minimum payments	40,349			1,301
Less: current portion	(6,760		)	(1,153		)
Lease obligations, noncurrent	$	33,589		$	148

Lease, Cost [Table Text Block]

The weighted average remaining lease term and the weighted average discount rate of our leases were as follows:



	March 31, 2019
Weighted average remaining lease term (years)
Operating leases	8
Finance leases	2
Weighted average discount rates
Operating leases	4.5	%
Finance leases	5.0	%

Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Employee stock-based compensation

The following table shows a summary of the stock-based compensation expense included in the condensed consolidated statements of operations for the three months ended March 31, 2019 and 2018:



	Three Months Ended
	March 31,
	2019		2018
	(in thousands)
Cost of revenues	$	545	$	654
Research and development	2,340		1,841
Sales and marketing	1,068		1,401
General and administrative	4,492		4,995
Total stock-based compensation	$	8,445	$	8,891

Stock option activity

A summary of the Company’s stock option activity is as follows:



	Outstanding Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
						(in thousands)
Balance as of December 31, 2018	3,429,309		$	31.79	6.4	$	149,935
Granted	103,275		$	94.45
Exercised	(152,164	)	$	26.59
Canceled	(33,355	)	$	50.49
Balance as of March 31, 2019	3,347,065		$	33.77	6.3	$	166,381
Vested and expected to vest - March 31, 2019	3,160,808		$	31.89	6.1	$	162,480
Exercisable - March 31, 2019	2,446,532		$	25.76	5.6	$	139,401

Restricted stock units activity

A summary of the Company’s RSU activity is as follows:



	Outstanding RSUs		Weighted Average Grant Date Fair Value Per Share

Balance as of December 31, 2018	1,226,883		$	55.71
Granted	124,857		$	79.69
Vested	(99,601	)	$	47.71
Canceled	(53,272	)	$	56.56
Balance as of March 31, 2019	1,198,867		$	58.83
Outstanding and expected to vest - March 31, 2019	883,174		$	57.74

Net Income Per Share (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The computations for basic and diluted net income per share are as follows:



	Three Months Ended
	March 31,
	2019		2018
	(in thousands, except per share data)
Numerator:
Net income	$	13,266	$	9,142
Denominator:
Weighted-average shares used in computing net income per share:
Basic	39,109		38,789
Effect of potentially dilutive securities:
Common stock options	1,970		2,503
Restricted stock units	467		642
Diluted	41,546		41,934
Net income per share:
Basic	$	0.34	$	0.24
Diluted	$	0.32	$	0.22

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

Potentially dilutive securities not included in the calculation of diluted net income per share because doing so would be antidilutive are as follows:



	Three Months Ended
	March 31,
	2019	2018
	(in thousands)
Common stock options	343	109
Restricted stock units	38	—
	381	109

Segment Information and Information about Geographic Area (Tables)

3 Months Ended

Mar. 31, 2019

Segment Reporting [Abstract]

Revenues be geographic area

Revenues by sales channel are as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Direct	$	43,039	$	38,710
Partner	32,304		26,168
Total	$	75,343	$	64,878

Revenues and property and equipment, net, by geographic area

ds):



	Three Month Ended March 31,
	2019		2018
United States	$	48,621	$	44,314
Foreign	26,722		20,564
Total	$	75,343	$	64,878

Property and equipment, net, by geographic area, are as fo

The Company and Summary of Significant Accounting Policies (Details) € in Millions, £ in Millions	3 Months Ended
	Sep. 30, 2018 USD ($)	Mar. 31, 2019 GBP (£)	Mar. 31, 2019 EUR (€)	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Reclassification
Operating Lease, Right-of-Use Asset				$ 29,604,000
Capitalization of internally developed software costs				200,000
Capitalized Computer Software, Unamortized				1,400,000		$ 1,200,000
Amortization expense for capitalized internally developed software	$ 100,000
Investment in privately held company	2,500,000
Retained earnings				34,488,000		27,964,000
Restricted cash	$ 1,200,000			1,200,000		$ 1,200,000
Operating Lease, Liability				$ 40,349,000
Operating Leases
Reclassification
Operating Lease, Right-of-Use Asset					$ 30,800,000
Operating Lease, Liability					41,600,000
Deferred Rent Receivables, Net					$ (3,900,000)
Foreign Exchange Contract [Member]
Reclassification
Derivative, notional amount		£ 8.0	€ 17.7

Fair Value of Financial Instruments - Cash and Cash Equivalents, Available-for-sale Securities Reconciliation (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost		$ 394,280	$ 366,421
Unrealized Gains		343	22
Unrealized Losses		(165)	(567)
Fair Value		394,458	365,876
Cash and cash equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost		93,127	41,026
Unrealized Gains		0	0
Unrealized Losses		0	0
Fair Value		93,127	41,026
Short-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost		205,074	248,324
Unrealized Gains		39	9
Unrealized Losses		(104)	(193)
Fair Value		205,009	248,140
Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost		96,079	77,071
Unrealized Gains		304	13
Unrealized Losses		(61)	(374)
Fair Value		96,322	76,710
Cash \| Cash and cash equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	$ 93,070		40,913
Unrealized Gains	0		0
Unrealized Losses	0		0
Fair Value		93,070	40,913
Money market funds \| Cash and cash equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	57		113
Unrealized Gains	0		0
Unrealized Losses	0		0
Fair Value		$ 57	113
Commercial paper \| Short-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost			3,237
Unrealized Gains			0
Unrealized Losses			0
Fair Value			3,237
Corporate bonds \| Short-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	38,990		30,906
Unrealized Gains	0		0
Unrealized Losses	(77)		(84)
Fair Value	38,913		30,822
Corporate bonds \| Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	27,279		35,322
Unrealized Gains	86		3
Unrealized Losses	(38)		(293)
Fair Value	27,327		35,032
Asset backed securities \| Short-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	9,868
Unrealized Gains	0
Unrealized Losses	0
Fair Value	9,868
Asset backed securities \| Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	37,588		22,945
Unrealized Gains	79		10
Unrealized Losses	(4)		(28)
Fair Value	37,663		22,927
US government agencies \| Short-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	156,216		203,734
Unrealized Gains	39		9
Unrealized Losses	(27)		(94)
Fair Value	156,228		203,649
US government agencies \| Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized Cost	31,212		18,804
Unrealized Gains	139		0
Unrealized Losses	(19)		(53)
Fair Value	$ 31,332		$ 18,751

Fair Value of Financial Instruments - Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 357,989	$ 343,544	$ 343,544
Change in net unrealized loss on available-for-sale marketable securities, net of tax	655	(407)
Amounts reclassified for net realized gain included in net income, net of tax	28	16
Other comprehensive income (loss), net	896	(391)
Ending balance	$ 373,403	366,319
Unrealized Gain (Loss) on Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ (545)	(545)
Change in net unrealized loss on available-for-sale marketable securities, net of tax			655
Amounts reclassified for net realized gain included in net income, net of tax			28
Other comprehensive income (loss), net			683
Ending balance			$ 138

Fair Value of Financial Instruments - Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	$ 301,331
Level 1 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value		$ 0	$ 0
Level 2 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value		301,331	324,850
Level 3 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value		0	0
Commercial paper \| Level 1 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value			0
Commercial paper \| Level 2 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value			3,237
Commercial paper \| Level 3 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value			0
US government agencies
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	187,560
US government agencies \| Level 1 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0		0
US government agencies \| Level 2 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	187,560		222,400
US government agencies \| Level 3 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0		0
Corporate bonds
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	66,240
Corporate bonds \| Level 1 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0		0
Corporate bonds \| Level 2 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	66,240		65,854
Corporate bonds \| Level 3 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0		0
Asset backed securities
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	47,531
Asset backed securities \| Level 1 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	0		0
Asset backed securities \| Level 2 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	47,531		33,359
Asset backed securities \| Level 3 \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value	$ 0		0
Fair Value \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value		301,331	324,850
Fair Value \| Commercial paper \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value			3,237
Fair Value \| US government agencies \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value		187,560	222,400
Fair Value \| Corporate bonds \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value		66,240	65,854
Fair Value \| Asset backed securities \| Recurring Basis
Assets, Fair Value Disclosure [Abstract]
Available-for-sale securities, fair value		$ 47,531	$ 33,359

Fair Value of Financial Instruments - Contractual Maturity (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Mature within One Year	$ 224,477
Mature after One Year through Two Years	50,000
Mature over Two Years	26,854
Fair Value	301,331
US government agencies
Schedule of Available-for-sale Securities [Line Items]
Mature within One Year	156,228
Mature after One Year through Two Years	16,736
Mature over Two Years	14,596
Fair Value	187,560
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Mature within One Year	38,913
Mature after One Year through Two Years	24,825
Mature over Two Years	2,502
Fair Value	66,240
Asset backed securities
Schedule of Available-for-sale Securities [Line Items]
Mature within One Year	29,336
Mature after One Year through Two Years	8,439
Mature over Two Years	9,756
Fair Value	$ 47,531

Fair Value of Financial Instruments - Derivatives (Details) € in Millions, £ in Millions	Sep. 30, 2018 GBP (£) contract	Sep. 30, 2018 EUR (€) contract	Dec. 31, 2017 GBP (£) contract	Dec. 31, 2017 EUR (€) contract	Dec. 31, 2017 USD ($) contract
Derivatives, Fair Value [Line Items]
Foreign currency contract, asset, fair value disclosure \| $					$ 0
Forward Contracts
Derivatives, Fair Value [Line Items]
Derivative, number of instruments held \| contract	8	8	2	2	2
Derivative, notional amount	£ 5.4	€ 13.0	£ 4.1	€ 12.9

Fair Value of Financial Instruments - Gains (Losses) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Other foreign currency transactions gain	$ 171	$ 810
Total foreign exchange loss, net	(160)	232
Forward Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net loss from forward contracts	$ (331)	$ (578)

Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 166,122				$ 160,672
Less: accumulated depreciation and amortization	(105,636)				(99,230)
Property and equipment, net	60,486		$ 60,486	$ 61,442	61,442
Depreciation and amortization expense	6,400	$ 6,400
Capital leases, accumulated depreciation	1,300
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	98,537				93,530
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	26,041				26,030
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	5,907				5,814
Finance leases - right of use asset
Property, Plant and Equipment [Line Items]
Property and equipment	3,503				3,503
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	15,665				15,356
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net				7,900	7,500
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment				$ 1,800	1,200
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 16,469				$ 16,439

Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 34,488					$ 27,964
Amortization of commissions assets		$ 400			$ 200
Revenue recognized	$ 75,343	75,343	$ 64,878	$ 64,878
Unbilled contracts		100,489			$ 100,489
Subscription Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized		$ 64,200		$ 55,600

Revenue from Contracts with Customers - Commission Asset Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018
Revenue from Contract with Customer [Abstract]
Commission asset, current	$ 1,691	$ 1,480
Commission asset, noncurrent	$ 5,087	$ 4,692

Revenue from Contracts with Customers - Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Accounts receivable	$ 68,516			$ 76,508
Allowance for doubtful accounts receivable	(653)		$ (653)	(683)	$ (816)
Total accounts receivable, net	$ 67,863	$ 75,825		$ 75,825

Revenue from Contracts with Customers - Unbilled contracts (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Deferred Revenue Arrangement [Line Items]
Contracts expected to be billed remainder of year	$ 46,413
Unbilled Receivables, Expected To Be Billed In 2019	35,226
Unbilled Receivables, Expected To Be Billed In 2020	15,727
Unbilled Receivables, Expected To Be Billed In 2021	2,098
Unbilled Receivables, Expected To Be Billed In 2022	902
Unbilled Receivables, Expected To Be Billed Thereafter	123
Unbilled Receivables, Not Billable	$ 100,489

Revenue from Contracts with Customers - Revenue by sales channel (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 75,343	$ 75,343	$ 64,878	$ 64,878
Direct
Disaggregation of Revenue [Line Items]
Revenues		43,039		38,710
Partner
Disaggregation of Revenue [Line Items]
Revenues		$ 32,304		$ 26,168

Business Combination - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 01, 2018	Dec. 31, 2018	Mar. 31, 2019	Sep. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 7,225	$ 7,325	$ 7,300	$ 7,200
1Mobility
Business Acquisition [Line Items]
Total purchase price		1,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		900
Goodwill		$ 100
Estimated useful life of technology-based intangible assets	15 years

Goodwill and Intangible Assets, Net - Carrying Value of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Goodwill and Intangible Assets [Line Items]
Cost	$ 27,743		$ 27,743				$ 26,843
Accumulated Amortization	(6,427)		(6,427)				(4,907)
Net Book Value	21,316		21,316				21,936
Intangible assets not subject to amortization	40		40				40
Total intangible assets, net	21,356		21,356		$ 21,356	$ 21,976	21,976
Amortization of intangible assets	1,500	$ 600
Goodwill	7,300		$ 7,300		$ 7,325	$ 7,225	7,200
Developed technology
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted Average Life (Years)			5 years
Weighted Average Remaining Life (Years)			3 years 6 months	3 years 9 months 18 days
Cost	26,356		$ 26,356				25,456
Accumulated Amortization	(5,580)		(5,580)				(4,085)
Net Book Value	20,776		$ 20,776				21,371
Patent licenses
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted Average Life (Years)			14 years
Weighted Average Remaining Life (Years)			5 years 4 months 24 days	5 years 10 months 24 days
Cost	1,387		$ 1,387				1,387
Accumulated Amortization	(847)		(847)				(822)
Net Book Value	$ 540		$ 540				$ 565

Goodwill and Intangible Assets, Net - Future Amortization (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
2019 (remaining nine months)	$ 4,561
2018	6,081
2019	6,081
2020	4,427
2021	100
2024 and thereafter	66
Net Book Value	$ 21,316	$ 21,936

Leases (Details) - USD ($)	1 Months Ended	3 Months Ended
Leases (Details) - USD ($)	Jan. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Jan. 01, 2018
Leases [Abstract]
Arrangement interest rate	5.00%
Lease, Expense		$ 1,600,000	$ 2,200,000
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year					$ 6,601,000
Operating Lease, Right-of-Use Asset		$ 29,604,000
Operating Lease, Weighted Average Remaining Lease Term		8 years
Finance Lease, Weighted Average Remaining Lease Term		2 years
Operating Lease, Weighted Average Discount Rate, Percent		4.50%
Finance Lease, Weighted Average Discount Rate, Percent		5.00%
Finance Lease, Right-of-Use Asset		$ 2,175,000
Lease, Right-of-Use Asset		31,779,000
Operating Lease, Liability, Current		(6,760,000)
Finance Lease, Liability, Current		(1,153,000)		$ (1,565,000)
Operating Lease, Liability, Noncurrent		33,589,000
Finance Lease, Liability, Noncurrent		148,000
Lease, Liability		41,650,000
Finance Lease, Liability, Payments, Remainder of Fiscal Year		1,328,000
Lessee, Operating Lease, Liability, Payments, Due Year Two					7,819,000
Finance Lease, Liability, Payments, Due Year Two		130,000
Lessee, Operating Lease, Liability, Payments, Due Year Three					6,124,000
Finance Lease, Liability, Payments, Due Year Three		54,000
Lessee, Operating Lease, Liability, Payments, Due Year Four					4,542,000
Finance Lease, Liability, Payments, Due Year Four		0
Lessee, Operating Lease, Liability, Payments, Due Year Five					4,298,000
Finance Lease, Liability, Payments, Due Year Five		0
Lessee, Operating Lease, Liability, Payments, Due after Year Five					19,299,000
Finance Lease, Liability, Payments, Due after Year Five		0
Lessee, Operating Lease, Liability, Payments, Due					$ 48,683,000
Finance Lease, Liability, Payments, Due		1,512,000
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		(8,334,000)
Finance Lease, Liability, Undiscounted Excess Amount		(211,000)
Operating Lease, Liability		40,349,000
Finance Lease, Liability		$ 1,301,000				$ 3,500,000

Commitments and Contingencies - Lease Narrative (Details)	1 Months Ended
	Jan. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Arrangement interest rate	5.00%

Stock-based Compensation - Stock Options (Details)	Sep. 30, 2018 shares
2012 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	3,827,360
2000 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	0

Stock-based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	$ 8,445	$ 8,891
Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized employee compensation cost	13,900		$ 13,900
Unrecognized employee compensation cost, period for recognition			2 years 1 month 6 days
Restricted Stock Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized employee compensation cost	52,600		$ 52,600
Unrecognized employee compensation cost, period for recognition			2 years 7 months 6 days
Cost of revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	545	654
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	2,340	1,841
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	1,068	1,401
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	$ 4,492	$ 4,995

Stock-based Compensation - Stock Option Plan Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Outstanding Shares
Beginning balance (in shares)	3,429,309
Granted (in shares)	103,275
Exercised (in shares)	(152,164)
Canceled (in shares)	(33,355)
Ending balance (in shares)	3,347,065
Vested and expected to vest (in shares)	3,160,808
Exercisable (in shares)	2,446,532
Weighted Average Exercise Price
Weighted average exercise price, Beginning balance (in dollars per share)	$ 31.79
Weighted average exercise price, granted (in dollars per share)	94.45
Weighted average exercise price, exercised (in dollars per share)	26.59
Weighted average exercise price, canceled (in dollars per share)	50.49
Weighted average exercise price, Ending balance (in dollars per share)	33.77
Weighted average exercise price, Vested and expected to vest (in dollars per share)	31.89
Weighted average exercise price, Exercisable (in dollars per share)	$ 25.76
Weighted Average Remaining Contractual Life
Weighted average remaining contractual life (in years)	6 years 3 months 18 days	6 years 4 months 24 days
Weighted Average Remaining Contractual Life (Years), Vested and Expected to Vest	6 years 1 month 6 days
Weighted Average Remaining Contractual Life (Years), Exercisable	5 years 7 months 6 days
Aggregate Intrinsic Value
Aggregate intrinsic value	$ 166,381		$ 149,935
Aggregate intrinsic value, Vested and expected to vest	162,480
Aggregate intrinsic value, Exercisable	$ 139,401

Stock-based Compensation - Restricted Stock (Details) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Outstanding RSUs
Beginning balance (in shares) \| shares	1,226,883
Granted (in shares) \| shares	124,857
Released (in shares) \| shares	(99,601)
Canceled (in shares) \| shares	(53,272)
Ending balance (in shares) \| shares	1,198,867
Outstanding and expected to vest (in shares) \| shares	883,174
Weighted Average Fair Value
Beginning balance (usd per share) \| $ / shares	$ 55.71
Granted (usd per share) \| $ / shares	79.69
Released (usd per share) \| $ / shares	47.71
Canceled (usd per share) \| $ / shares	56.56
Ending balance (usd per share) \| $ / shares	58.83
Outstanding and expected to vest (usd per share) \| $ / shares	$ 57.74

Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017
Numerator:
Net income	$ 13,266		$ 9,142
Denominator:
Basic (shares)	39,109		38,789
Common stock options (shares)		1,970		2,503
Restricted stock units (shares)		467		642
Diluted (shares)	41,546		41,934
Basic (USD per share)	$ 0.34		$ 0.24
Diluted (USD per share)	$ 0.32		$ 0.22
Antidilutive Securities
Antidilutive securities (shares)		381		109
Stock Options
Antidilutive Securities
Antidilutive securities (shares)		343		109
Restricted Stock Units
Antidilutive Securities
Antidilutive securities (shares)		38		0

Stockholder's Equity (Details) - USD ($)	3 Months Ended
Stockholder's Equity (Details) - USD ($)	Sep. 30, 2018	Feb. 05, 2018
Equity [Abstract]
Share repurchase program, authorized amount		$ 100,000,000
Shares repurchased during period (in shares)	94,090
Shares repurchased during period, value	$ 7,900,000
Remaining authorized amount	$ 107,100,000

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 2,571		$ 509
Effective tax rate		16.20%		5.30%
Unrecognized Tax Benefits		$ 6,900			$ 6,400
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 3,800			$ 3,500

Segment Information and Information about Geographic Area - Revenue by geographic area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 75,343	$ 75,343	$ 64,878	$ 64,878
United States
Disaggregation of Revenue [Line Items]
Revenues		48,621		44,314
Foreign
Disaggregation of Revenue [Line Items]
Revenues		$ 26,722		$ 20,564

Segment Information and Information about Geographic Area - Property and Equipment, net (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) segment	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments (in segment) \| segment	1
Property and equipment, net	$ 60,486	$ 60,486	$ 61,442	$ 61,442
United States
Segment Reporting Information [Line Items]
Property and equipment, net	57,810			59,222
Other
Segment Reporting Information [Line Items]
Property and equipment, net	$ 2,676			$ 2,220

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 2,711,000
Retained Earnings [Member]
Retained Earnings (Accumulated Deficit)	us-gaap_RetainedEarningsAccumulatedDeficit	$ 2,711,000