Qualys (QLYS) 10-Q 2 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 30, 2019
Document and Entity Information [Abstract]
Title of 12(b) Security	Common stock, $0.001 par value per share
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Entity Registrant Name	QUALYS, INC.
Entity Address, Address Line One	919 E. Hillsdale Boulevard, 4th Floor
City Area Code	650
Local Phone Number	801-6100
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Central Index Key	0001107843
Document Type	10-Q
Entity File Number	001-35662
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		39,238,573
Entity Tax Identification Number	77-0534145
Trading Symbol	QLYS
Security Exchange Name	NASDAQ
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Address, City or Town	Foster City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94404

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 91,381,000	$ 41,026,000
Short-term marketable securities	207,626,000	248,140,000
Accounts receivable, net of allowance of $648 and $683 as of June 30, 2019 and December 31, 2018, respectively	63,184,000	75,825,000
Prepaid expenses and other current assets	19,395,000	13,974,000
Total current assets	381,586,000	378,965,000
Long-term marketable securities	111,521,000	76,710,000
Property and equipment, net	59,359,000	61,442,000
Operating Lease, Right-of-Use Asset	28,101,000
Deferred tax assets, net	22,976,000	26,387,000
Intangible assets, net	19,836,000	21,976,000
Goodwill	7,325,000	7,225,000
Restricted cash	1,200,000	1,200,000
Other noncurrent assets	13,708,000	11,775,000
Total assets	645,612,000	585,680,000
Current liabilities :
Accounts payable	963,000	5,588,000
Accrued liabilities	24,315,000	26,695,000
Contract with Customer, Liability, Current	176,609,000	164,624,000
Finance Lease, Liability, Current	6,826,000	0
Operating Lease, Liability, Noncurrent	31,987,000
Total current liabilities	208,713,000	196,907,000
Contract with Customer, Liability, Noncurrent	20,835,000	20,423,000
Other noncurrent liabilities	479,000	10,361,000
Total liabilities	262,014,000	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 June 30, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value; 1,000,000,000 shares authorized; 39,224,075 and 39,015,034 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	39,000	39,000
Additional paid-in capital	345,637,000	330,572,000
Accumulated other comprehensive income (loss)	1,240,000	(586,000)
Retained earnings	36,682,000	27,964,000
Total stockholders’ equity	383,598,000	357,989,000
Total liabilities and stockholders’ equity	$ 645,612,000	$ 585,680,000

Consolidated Statements of Stoc

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)
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)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(63,695)
Issuance of common stock upon vesting of restricted stock units (in shares)		158,561
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]
Net income	19,435
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(247)
Change in unrealized loss on investments	0
Ending balance at Jun. 30, 2018	365,239	$ 39	320,226	(821)	45,795
Balance (in shares) at Jun. 30, 2018		38,985,798
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	$ 29,498
Issuance of common stock upon exercise of stock options (shares)	344,851
Beginning balance at Mar. 31, 2018	$ 366,319	$ 39	316,694	(965)	50,551
Balance (in shares) at Mar. 31, 2018		38,957,692
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,293				10,293
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	144			144
Change in unrealized loss on investments	0
Issuance of common stock upon exercise of stock options	4,239		4,239
Issuance of common stock upon exercise of stock options (shares)		144,851
Stock Repurchased During Period, Shares		(235,539)
Treasury Stock, Value, Acquired, Cost Method	(17,875)		(2,826)		(15,049)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(65,214)
Issuance of common stock upon vesting of restricted stock units (in shares)		184,008
Taxes from release of the restricted share units	(4,904)		(4,904)
Stock-based compensation	7,023		7,023
Ending balance at Jun. 30, 2018	365,239	$ 39	320,226	(821)	45,795
Balance (in shares) at Jun. 30, 2018		38,985,798
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings (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
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)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(38,877)
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
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	29,498
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,826
Change in unrealized loss on investments	404
Ending balance at Jun. 30, 2019	383,598	$ 39	345,637	1,240	36,682
Balance (in shares) at Jun. 30, 2019		39,224,075
Beginning 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]
Net income	16,232				16,232
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	930			930
Change in unrealized loss on investments	191
Issuance of common stock upon exercise of stock options	4,944		4,944
Issuance of common stock upon exercise of stock options (shares)		192,687
Stock Repurchased During Period, Shares		(183,948)
Treasury Stock, Value, Acquired, Cost Method	(16,245)		(2,207)		(14,038)
Adjustment To Additional Paid In Capital, Share-Based Compensation, Taxes Related To Net Share Settlements Of Equity Awards		(45,250)
Issuance of common stock upon vesting of restricted stock units (in shares)		126,754
Taxes from release of the restricted share units	(4,044)		(4,044)
Stock-based compensation	8,378		8,378
Ending balance at Jun. 30, 2019	383,598	$ 39	$ 345,637	$ 1,240	$ 36,682
Balance (in shares) at Jun. 30, 2019		39,224,075
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings (Accumulated Deficit)	$ 36,682

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 648	$ 683
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	39,224,075	39,015,034
Common stock, shares outstanding	39,224,075	39,015,034

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues
Revenues	$ 78,929	$ 68,153	$ 154,272	$ 133,031
Cost of revenues	17,537	16,248	35,246	32,149
Gross profit	61,392	51,905	119,026	100,882
Operating expenses:
Research and development	17,695	13,128	33,532	25,681
Sales and marketing	17,165	18,976	34,480	35,209
General and administrative	10,424	8,906	20,855	20,691
Total operating expenses	45,284	41,010	88,867	81,581
Income from operations	16,108	10,895	30,159	19,301
Other income (expense), net:
Interest expense	(28)	(39)	70	77
Interest income	2,198	1,452	4,249	2,542
Other income (expense), net	231	(529)	8	(336)
Total other income, net	2,401	884	4,187	2,129
Income before income taxes	18,509	11,779	34,346	21,430
Provision for income taxes	2,277	1,486	4,848	1,995
Net income	$ 16,232	$ 10,293	$ 29,498	$ 19,435
Net income per share:
Basic (USD per share)	$ 0.41	$ 0.26	$ 0.75	$ 0.50
Diluted (USD per share)	$ 0.39	$ 0.24	$ 0.71	$ 0.46
Weighted average shares used in computing net income per share:
Basic (shares)	39,198	38,987	39,143	38,843
Diluted (shares)	41,530	42,215	41,570	42,074

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income	$ 16,232	$ 10,293	$ 29,498	$ 19,435
Available-for-sale marketable securities:
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments, after Tax	724	65	1,379	(342)
Reclassification adjustment for net realized gain included in net income	15	79	43	95
Change in net unrealized gain (loss) on marketable securities, net of tax	739	144	1,422	(247)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	43	0	(37)	0
Total change in unrealized gain (loss) on marketable securities, net of tax	191	0	404	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	930	144	1,826	(247)
Comprehensive income	17,162	10,437	31,324	19,188
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Available-for-sale marketable securities:
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	$ 148	$ 0	$ 441	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		9 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 16,232	$ 13,266	$ 10,293	$ 9,142	$ 29,498	$ 19,435	$ 29,498
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense					15,809	14,249
Provision for Doubtful Accounts					86	0
Loss on disposal of property and equipment					(183)	(9)
Stock-based compensation					16,780	15,914
Amortization of premiums and (accretion) of discounts on marketable securities					1,060	169
Deferred income taxes					3,047	681
Changes in operating assets and liabilities:
Accounts receivable					(12,555)	(11,876)
Prepaid expenses and other assets					6,863	4,073
Accounts payable					(1,189)	(331)
Accrued liabilities					(121)	6,238
Deferred revenues					12,397	4,424
Other non-current liabilities					153	(1,026)
Net cash provided by operating activities					81,275	67,227
Cash flows from investing activities:
Purchases of marketable securities					184,829	151,825
Sales and maturities of marketable securities					193,270	120,838
Purchases of property and equipment					14,138	13,240
Business combinations					(1,850)	(3,359)
Payments to Acquire Investments					0	(2,500)
Net cash used in investing activities					(7,547)	(50,086)
Cash flows from financing activities:
Proceeds from exercise of stock options					8,991	12,174
Payments for taxes related to net share settlement of equity awards					7,411	8,935
Principal payments under finance lease obligations					836	794
Repurchase of common stock					24,117	19,356
Net cash used in financing activities					(23,373)	(16,911)
Effect of Exchange Rate on Cash and Cash Equivalents, Continuing Operations					0	(42)
Net increase in cash, cash equivalents and restricted cash					50,355	188
Cash, cash equivalents and restricted cash at beginning of period		$ 42,226		$ 87,791	42,226	87,791	$ 87,791
Cash, cash equivalents and restricted cash at end of period	$ 92,581		$ 87,979		$ 92,581	$ 87,979

The Company and Summary of Sign

The Company and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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 condensed consolidated balance sheets. Gains and losses resulting from currency exchange rate movements on non-designated forward contracts are recognized in other income (expense), net. 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 unaudited condensed consolidated financial statements. The cash flow effects of the Company's derivative contracts for the six months ended June 30, 2019 were included within net cash provided by operating activities on its condensed consolidated statements of cash flows. As of June 30, 2019 , the Company had €18.9 million and £9.2 million of notional amounts outstanding on foreign currency ("FX") contracts designated as cash flow hedges. The Company had no hedges designated as cash flow hedges as of June 30, 2018 . Stock-Based Compensation The Company recognizes the fair value of its employee stock options and restricted stock units 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. The Company has issued performance-based awards and accounts for these awards as stock-based compensation with multiple performance conditions. For these performance-based awards, 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. For the three and six months ended June 30, 2019 , the Company recorded approximately $0.2 million and $0.5 million of stock-based compensation cost for these awards, respectively. 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. Upon general release, such costs are amortized on a straight-line basis over an 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 and $0.4 million for the three and six months ended June 30, 2019 , respectively. Unamortized cost for capitalized internally developed software was $1.6 million at June 30, 2019 and $1.2 million at December 31, 2018 . Amortization expense for capitalized internally developed software was insignificant for the three and six months ended June 30, 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 preferred stock of a privately-held company. The investment has been accounted for using the cost method and included in other noncurrent 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. During the three months ended June 30, 2019 , the Company made an advance payment of $0.6 million to the investee for certain development work, which is recorded in other noncurrent assets on the condensed consolidated balance sheet . Recently Adopted Accounting Pronouncements In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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 ("ROU") 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 January 1, 2019, $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. The Company also elected to make the accounting policy election for short-term leases, permitting the Company to not apply the recognition requirements of this standard to short-term leases with terms of 12 months or less. 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 as of January 1, 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 adopted this ASU during the first quarter of fiscal 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 Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
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 usi ng 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. As of June 30, 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: June 30, 2019 Amortized Cost Unrealized Gains Unrealized (Losses) Fair Value (in thousands) Cash and cash equivalents: Cash $ 90,154 $ — $ — $ 90,154 Money market funds 727 — — 727 Commercial paper 500 — — 500 Total 91,381 — — 91,381 Short-term marketable securities : Corporate bonds 36,252 46 (39 ) 36,259 Asset-backed securities 8,840 1 (1 ) 8,840 U.S. government agencies 162,356 179 (8 ) 162,527 Total 207,448 226 (48 ) 207,626 Long-term marketable securities : Asset-backed securities 40,833 244 — 41,077 U.S. government agencies 44,351 483 — 44,834 Corporate bonds 25,382 228 — 25,610 Total 110,566 955 — 111,521 Total $ 409,395 $ 1,181 $ (48 ) $ 410,528 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 AOCI related to available-for-sale marketable securities for the six months ended June 30, 2019 (in thousands): Unrealized Gain (Loss), net AOCI for available-for sale marketable securities balance at December 31, 2018 $ (545 ) Change in net unrealized gain, net of tax 1,379 Amounts reclassified for net realized gain included in net income 43 Total change in unrealized gain (loss), net of tax 1,422 AOCI for available-for sale marketable securities balance at June 30, 2019 $ 877 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: June 30, 2019 Level 1 Level 2 Level 3 Fair Value (in thousands) Commercial paper $ — $ 500 $ — $ 500 U.S. government agencies — 207,361 — 207,361 Corporate bonds — 61,869 — 61,869 Asset-backed securities — 49,917 — 49,917 Total $ — $ 319,647 $ — $ 319,647 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: June 30, 2019 Mature within One Year Mature after One Year through Two Years Mature over Two Years Fair Value (in thousands) Commercial paper $ 500 $ — $ — $ 500 U.S. government agencies 162,527 30,192 14,642 207,361 Corporate bonds 36,258 19,651 5,960 61,869 Asset-backed securities 30,329 14,678 4,910 49,917 Total $ 229,614 $ 64,521 $ 25,512 $ 319,647 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, as well as to manage foreign currency fluctuation risk related to forecasted transactions. Non-designated forward contracts At June 30, 2019 , the Company had five outstanding forward contracts with notional amounts of €10.0 million and £4.0 million . At December 31, 2018, the Company had two outstanding forward contracts with notional amounts of €16.0 million and £6.3 million . Designated cash flow hedge contracts At June 30, 2019 , the Company had 26 open cash flow hedge contracts with notional amounts of €18.9 million and £9.2 million . During the three and six months ended June 30, 2019 , the Company recorded unrealized FX gains related to these contracts in AOCI of $0.2 million and $0.4 million , respectively, net of tax. The Company did not have any unrealized FX gains or losses during the three and six months ended June 30, 2018, respectively. At December 31, 2018, the Company had two open cash flow hedge contracts with notional amounts of €12.9 million and £4.1 million . 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 Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands) Net gain (loss) from forward contracts $ 44 $ 890 $ 78 $ 314 Other foreign currency transactions gain (loss) 249 (1,357 ) 55 (549 ) Total foreign exchange gain (loss), net $ 293 $ (467 ) $ 133 $ (235 )

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net, which includes assets under finance lease, consists of the following: June 30, December 31, 2019 2018 (in thousands) Computer equipment $ 102,868 $ 93,530 Computer software 26,788 26,030 Furniture, fixtures and equipment 5,966 5,814 Finance leases - right of use asset 3,503 3,503 Scanner appliances 15,349 15,356 Leasehold improvements 16,468 16,439 Total property and equipment 170,942 160,672 Less: accumulated depreciation and amortization (111,583 ) (99,230 ) Property and equipment, net $ 59,359 $ 61,442 Physical scanner appliances and other computer equipment have a net carrying value of $6.0 million and $7.9 million at June 30, 2019 and December 31, 2018 , respectively, including assets that have not been placed in service of $0.9 million and $1.8 million , respectively. Depreciation and amortization expense relating to property and equipment, including capitalized leases, was $6.3 million and $6.4 million for the three months ended June 30, 2019 and 2018 , respectively, and $12.7 million and $12.8 million for the six months ended June 30, 2019 and 2018, respectively. Accumulated depreciation under finance leases was $1.6 million at June 30, 2019 .

Revenue from Contracts with Cus

Revenue from Contracts with Customers	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers The Company's subscription contracts are 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 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 separate performance obligations. In the rare case that allocation of the transaction price is needed, 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. For contracts that include leased scanners and PCPs, we apply the lease and non-lease component practical expedient under ASC 842 to account for non-lease components and lease components as combined components under the revenue recognition guidance in ASU 2014-09, "Revenue from Contracts with Customers" (Topic 606) as the subscriptions are the predominant components in the arrangements. 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 elected the practical expedient to expense commissions on renewals where the specific anticipated contract term amortization period is one year or less. 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): June 30, 2019 December 31, 2018 Commission asset, current $ 1,958 $ 1,480 Commission asset, noncurrent $ 5,662 $ 4,692 For the three months ended June 30, 2019 and 2018 , the Company recognized $0.5 million and $0.3 million , respectively, of commission expense from amortization of its commission assets. For the six months ended June 30, 2019 and 2018 , the Company recognized $0.9 million and $0.5 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. Revenue of $49.1 million and $42.8 million was recognized during the three months ended June 30, 2019 and 2018 , respectively, which amounts were included in the deferred revenue balances as of December 31, 2018 and 2017, respectively. Revenue of $113.3 million and $98.4 million was recognized during the six months ended June 30, 2019 and 2018 , respectively, which amounts were included in the deferred revenue balances as of December 31, 2018 and 2017, respectively. The Company's payment terms vary by the type and location of its customer and the products or services offered. 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 June 30, 2019 (in thousands): Total Expected Revenue 2019 (remaining six months) $ 36,395 2020 46,266 2021 20,830 2022 4,230 2023 1,150 2024 and thereafter 268 Total $ 109,139

Business Combination Business C

Business Combination Business Combination	6 Months Ended
	Jun. 30, 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,

Goodwill and Intangible Assets, Net	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets, Net	ngible 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): June 30, 2019 Weighted Average Life (Years) Weighted Average Remaining Life (Years) Cost Accumulated Amortization Net Book Value Developed technology 5 3.2 $ 26,356 $ (7,076 ) $ 19,280 Patent licenses 14 5.2 1,387 (871 ) 516 Total intangibles subject to amortization $ 27,743 $ (7,947 ) 19,796 Intangible assets not subject to amortization 40 Total intangible assets, net $ 19,836 December 31, 2018 Weighted Average Life (Years) Weighted Average Remaining Life (Years) Cost Accumulated Amortization Net Book Value Developed technology 5 3.8 $ 25,456 $ (4,085 ) $ 21,371 Patent Licenses 14 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 $0.9 million for the three months ended June 30, 2019 and 2018 , respectively, and $3.0 million and $1.5 million for the six months ended June 30, 2019 and 2018, respectively. As of June 30, 2019 , the Company expects amortization expense in future periods to be as follows (in thousands): Amortization Expense 2019 (remaining six months) $ 3,041 2020 6,081 2021 6,081 2022 4,427 2023 100 2024 and thereafter 66 Total expected future amortization expense $ 19,796

Leases (Notes)

Leases (Notes)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	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 apply the lease and non-lease component practical expedient and we account for lease components (e.g., customer premise equipment) and non-lease components (e.g., service revenue) as combined components and account for the combined components under the revenue recognition guidance in 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. June 30, (in thousands) Classification on the Balance Sheet 2019 Assets Operating lease assets Operating lease - right of use asset $ 28,101 Finance lease assets Property and equipment, net 1,883 Total lease assets $ 29,984 Liabilities Current Operating Operating lease liabilities, current $ 6,826 Finance Accrued liabilities 741 Noncurrent Operating Operating lease liabilities, noncurrent 31,987 Finance Other noncurrent liabilities 117 Total lease liabilities $ 39,671 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 June 30, 2019 (in thousands): Operating Leases Finance Leases (in thousands) 2019 (remaining six months) $ 4,502 $ 885 2020 7,845 130 2021 6,137 54 2022 4,544 — 2023 4,299 — 2024 and thereafter 19,299 — Total minimum lease payments 46,626 1,069 Less: amount representing interest 7,813 211 Present value of minimum payments 38,813 858 Less: current portion (6,826 ) (741 ) Lease obligations, noncurrent $ 31,987 $ 117 Lease expense was $2.0 million and $1.3 million for the three months ended June 30, 2019 and 2018 , respectively, and $3.6 million and $2.5 million for the six months ended June 30, 2019 and 2018, respectively. The weighted average remaining lease term and the weighted average discount rate of our leases were as follows: June 30, 2019 Weighted average remaining lease term (years) Operating leases 7 Finance leases 1 Weighted average discount rates Operating leases 4.6 % Finance leases 5.0 %
Leases	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 apply the lease and non-lease component practical expedient and we account for lease components (e.g., customer premise equipment) and non-lease components (e.g., service revenue) as combined components and account for the combined components under the revenue recognition guidance in 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. June 30, (in thousands) Classification on the Balance Sheet 2019 Assets Operating lease assets Operating lease - right of use asset $ 28,101 Finance lease assets Property and equipment, net 1,883 Total lease assets $ 29,984 Liabilities Current Operating Operating lease liabilities, current $ 6,826 Finance Accrued liabilities 741 Noncurrent Operating Operating lease liabilities, noncurrent 31,987 Finance Other noncurrent liabilities 117 Total lease liabilities $ 39,671 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 June 30, 2019 (in thousands): Operating Leases Finance Leases (in thousands) 2019 (remaining six months) $ 4,502 $ 885 2020 7,845 130 2021 6,137 54 2022 4,544 — 2023 4,299 — 2024 and thereafter 19,299 — Total minimum lease payments 46,626 1,069 Less: amount representing interest 7,813 211 Present value of minimum payments 38,813 858 Less: current portion (6,826 ) (741 ) Lease obligations, noncurrent $ 31,987 $ 117 Lease expense was $2.0 million and $1.3 million for the three months ended June 30, 2019 and 2018 , respectively, and $3.6 million and $2.5 million for the six months ended June 30, 2019 and 2018, respectively. The weighted average remaining lease term and the weighted average discount rate of our leases were as follows: June 30, 2019 Weighted average remaining lease term (years) Operating leases 7 Finance leases 1 Weighted average discount rates Operating leases 4.6 % Finance leases 5.0 %

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 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

Stock-based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based Compensation	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 11.8 million shares of common stock as of June 30, 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 June 30, 2019 , 5.6 million 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 and six months ended June 30, 2019 and 2018 : Three Months Ended Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands) Cost of revenues $ 552 $ 609 $ 1,097 $ 1,263 Research and development 2,704 1,976 5,044 3,817 Sales and marketing 1,063 1,105 2,131 2,506 General and administrative 4,016 3,333 8,508 8,328 Total stock-based compensation $ 8,335 $ 7,023 $ 16,780 $ 15,914 As of June 30, 2019 , the Company had $13.2 million of total unrecognized stock-based compensation cost related to unvested options that it expects to recognize over a weighted-average period of 2.2 years , and $50.7 million of unrecognized stock-based compensation cost related to unvested RSUs that it expects to recognize over a weighted-average period of 2.5 years . Compensation cost is recognized 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 191,875 $ 91.13 Exercised (344,851 ) $ 26.07 Canceled (90,932 ) $ 66.12 Balance as of June 30, 2019 3,185,401 $ 35.00 6.2 $ 167,275 Vested and expected to vest - June 30, 2019 3,021,949 $ 33.04 6.0 $ 164,336 Exercisable - June 30, 2019 2,399,078 $ 26.85 5.5 $ 144,641 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 194,944 $ 82.33 Vested (226,355 ) $ 53.35 Canceled (91,429 ) $ 62.26 Balance as of June 30, 2019 1,104,043 $ 60.38 Outstanding and expected to vest - June 30, 2019 822,916 $ 59.03

Net Income Per Share

Net Income Per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Income Per Share	Net Income Per Share The computations for basic and diluted net income per share are as follows: Three Months Ended Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands, except per share data) Numerator: Net income $ 16,232 $ 10,293 $ 29,498 $ 19,435 Denominator: Weighted-average shares used in computing net income per share: Basic 39,198 38,987 39,143 38,843 Effect of potentially dilutive securities: Common stock options 1,890 2,610 1,950 2,576 Restricted stock units 442 618 477 655 Diluted 41,530 42,215 41,570 42,074 Net income per share: Basic $ 0.41 $ 0.26 $ 0.75 $ 0.50 Diluted $ 0.39 $ 0.24 $ 0.71 $ 0.46 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 Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands) Common stock options 419 125 381 81 Restricted stock units 54 2 62 30 473 127 443 111

Stockholder's Equity

Stockholder's Equity	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2019 , the Company repurchased 278,038 shares of its common stock for approximately $24.1 million . All share repurchases were made using cash resources. As of June 30, 2019 , approximately $90.8 million

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 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 $2.3 million and income tax provision of $1.5 million for the three months ended June 30, 2019 and 2018 , respectively, resulting in an effective tax rate of 12.3% and 12.6% , respectively. The tax provision for the three months ended June 30, 2019 as compared to the tax provision for the three months ended June 30, 2018 changed primarily due to an increase in pre-tax income in the current period. As of June 30, 2019 , the Company had unrecognized tax benefits of $7.4 million , of which $4.1 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 Informa

Segment Information and Information about Geographic Area	6 Months Ended
	Jun. 30, 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 Months Ended Six Months Ended June 30, June 30, 2019 2018 2019 2018 United States $ 50,704 $ 45,799 $ 99,325 $ 90,113 Foreign 28,225 22,354 54,947 42,918 Total $ 78,929 $ 68,153 $ 154,272 $ 133,031 Property and equipment, net, by geographic area, are as follows: June 30, December 31, 2019 2018 (in thousands) United States $ 56,511 $ 59,222 Foreign 2,848 2,220 Total property and equipment, net $ 59,359 $ 61,442

The Company and Summary of Si_2

The Company and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 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 condensed consolidated balance sheets. Gains and losses resulting from currency exchange rate movements on non-designated forward contracts are recognized in other income (expense), net. 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 unaudited condensed consolidated financial statements. The cash flow effects of the Company's derivative contracts for the six months ended June 30, 2019 were included within net cash provided by operating activities on its condensed consolidated statements of cash flows. As of June 30, 2019 , the Company had €18.9 million and £9.2 million of notional amounts outstanding on foreign currency ("FX") contracts designated as cash flow hedges. The Company had no hedges designated as cash flow hedges as of June 30, 2018 . Stock-Based Compensation The Company recognizes the fair value of its employee stock options and restricted stock units 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. The Company has issued performance-based awards and accounts for these awards as stock-based compensation with multiple performance conditions. For these performance-based awards, 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. For the three and six months ended June 30, 2019 , the Company recorded approximately $0.2 million and $0.5 million of stock-based compensation cost for these awards, respectively. 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. Upon general release, such costs are amortized on a straight-line basis over an 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 and $0.4 million for the three and six months ended June 30, 2019 , respectively. Unamortized cost for capitalized internally developed software was $1.6 million at June 30, 2019 and $1.2 million at December 31, 2018 . Amortization expense for capitalized internally developed software was insignificant for the three and six months ended June 30, 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 preferred stock of a privately-held company. The investment has been accounted for using the cost method and included in other noncurrent 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. During the three months ended June 30, 2019 , the Company made an advance payment of $0.6 million to the investee for certain development work, which is recorded in other noncurrent assets on the condensed consolidated balance sheet . Recently Adopted Accounting Pronouncements
Recently adopted Accounting Pronouncements and Recent Accounting Pronouncements	In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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 ("ROU") 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 January 1, 2019, $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. The Company also elected to make the accounting policy election for short-term leases, permitting the Company to not apply the recognition requirements of this standard to short-term leases with terms of 12 months or less. 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 as of January 1, 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 adopted this ASU during the first quarter of fiscal 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 usi ng 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. As of June 30, 2019 , management estimated the fair value of such commitments to be zero.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 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: June 30, 2019 Amortized Cost Unrealized Gains Unrealized (Losses) Fair Value (in thousands) Cash and cash equivalents: Cash $ 90,154 $ — $ — $ 90,154 Money market funds 727 — — 727 Commercial paper 500 — — 500 Total 91,381 — — 91,381 Short-term marketable securities : Corporate bonds 36,252 46 (39 ) 36,259 Asset-backed securities 8,840 1 (1 ) 8,840 U.S. government agencies 162,356 179 (8 ) 162,527 Total 207,448 226 (48 ) 207,626 Long-term marketable securities : Asset-backed securities 40,833 244 — 41,077 U.S. government agencies 44,351 483 — 44,834 Corporate bonds 25,382 228 — 25,610 Total 110,566 955 — 111,521 Total $ 409,395 $ 1,181 $ (48 ) $ 410,528 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 AOCI related to available-for-sale marketable securities for the six months ended June 30, 2019 (in thousands): Unrealized Gain (Loss), net AOCI for available-for sale marketable securities balance at December 31, 2018 $ (545 ) Change in net unrealized gain, net of tax 1,379 Amounts reclassified for net realized gain included in net income 43 Total change in unrealized gain (loss), net of tax 1,422 AOCI for available-for sale marketable securities balance at June 30, 2019 $ 877
Schedule of Assets Measured on Recurring Basis	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: June 30, 2019 Level 1 Level 2 Level 3 Fair Value (in thousands) Commercial paper $ — $ 500 $ — $ 500 U.S. government agencies — 207,361 — 207,361 Corporate bonds — 61,869 — 61,869 Asset-backed securities — 49,917 — 49,917 Total $ — $ 319,647 $ — $ 319,647 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: June 30, 2019 Mature within One Year Mature after One Year through Two Years Mature over Two Years Fair Value (in thousands) Commercial paper $ 500 $ — $ — $ 500 U.S. government agencies 162,527 30,192 14,642 207,361 Corporate bonds 36,258 19,651 5,960 61,869 Asset-backed securities 30,329 14,678 4,910 49,917 Total $ 229,614 $ 64,521 $ 25,512 $ 319,647
Summary of Gains (Losses) Recognized From Forward Contracts and Other Foreign Currency Transactions	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 Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands) Net gain (loss) from forward contracts $ 44 $ 890 $ 78 $ 314 Other foreign currency transactions gain (loss) 249 (1,357 ) 55 (549 ) Total foreign exchange gain (loss), net $ 293 $ (467 ) $ 133 $ (235 )

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Property and equipment, net	Property and equipment, net, which includes assets under finance lease, consists of the following: June 30, December 31, 2019 2018 (in thousands) Computer equipment $ 102,868 $ 93,530 Computer software 26,788 26,030 Furniture, fixtures and equipment 5,966 5,814 Finance leases - right of use asset 3,503 3,503 Scanner appliances 15,349 15,356 Leasehold improvements 16,468 16,439 Total property and equipment 170,942 160,672 Less: accumulated depreciation and amortization (111,583 ) (99,230 ) Property and equipment, net $ 59,359 $ 61,442

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Commission asset balances	Commission asset balances are as follows (in thousands): June 30, 2019 December 31, 2018 Commission asset, current $ 1,958 $ 1,480 Commission asset, noncurrent $ 5,662 $ 4,692
Contract liabilities
Accounts receivable, net
Expected revenue from contracts	The following table sets forth the expected revenue from all remaining performance obligations as of June 30, 2019 (in thousands): Total Expected Revenue 2019 (remaining six months) $ 36,395 2020 46,266 2021 20,830 2022 4,230 2023 1,150 2024 and thereafter 268 Total $ 109,139
Revenue by sales channel	Revenues by sales channel are as follows (in thousands): Three Months Ended Six Months Ended June 30, June 30, 2019 2018 2019 2018 Direct $ 45,672 $ 35,294 $ 88,711 $ 74,004 Partner 33,257 32,859 65,561 59,027 Total $ 78,929 $ 68,153 $ 154,272 $ 133,031

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets, Net (Tables)	6 Months Ended
	Jun. 30, 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): June 30, 2019 Weighted Average Life (Years) Weighted Average Remaining Life (Years) Cost Accumulated Amortization Net Book Value Developed technology 5 3.2 $ 26,356 $ (7,076 ) $ 19,280 Patent licenses 14 5.2 1,387 (871 ) 516 Total intangibles subject to amortization $ 27,743 $ (7,947 ) 19,796 Intangible assets not subject to amortization 40 Total intangible assets, net $ 19,836 December 31, 2018 Weighted Average Life (Years) Weighted Average Remaining Life (Years) Cost Accumulated Amortization Net Book Value Developed technology 5 3.8 $ 25,456 $ (4,085 ) $ 21,371 Patent Licenses 14 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 June 30, 2019

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 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. June 30, (in thousands) Classification on the Balance Sheet 2019 Assets Operating lease assets Operating lease - right of use asset $ 28,101 Finance lease assets Property and equipment, net 1,883 Total lease assets $ 29,984 Liabilities Current Operating Operating lease liabilities, current $ 6,826 Finance Accrued liabilities 741 Noncurrent Operating Operating lease liabilities, noncurrent 31,987 Finance Other noncurrent liabilities 117 Total lease liabilities $ 39,671
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	The following are the minimum annual lease payments due under these leases at June 30, 2019 (in thousands): Operating Leases Finance Leases (in thousands) 2019 (remaining six months) $ 4,502 $ 885 2020 7,845 130 2021 6,137 54 2022 4,544 — 2023 4,299 — 2024 and thereafter 19,299 — Total minimum lease payments 46,626 1,069 Less: amount representing interest 7,813 211 Present value of minimum payments 38,813 858 Less: current portion (6,826 ) (741 ) Lease obligations, noncurrent $ 31,987 $ 117
Finance Lease, Liability, Maturity [Table Text Block]	The following are the minimum annual lease payments due under these leases at June 30, 2019 (in thousands): Operating Leases Finance Leases (in thousands) 2019 (remaining six months) $ 4,502 $ 885 2020 7,845 130 2021 6,137 54 2022 4,544 — 2023 4,299 — 2024 and thereafter 19,299 — Total minimum lease payments 46,626 1,069 Less: amount representing interest 7,813 211 Present value of minimum payments 38,813 858 Less: current portion (6,826 ) (741 ) Lease obligations, noncurrent $ 31,987 $ 117
Lease, Cost [Table Text Block]	The weighted average remaining lease term and the weighted average discount rate of our leases were as follows: June 30, 2019 Weighted average remaining lease term (years) Operating leases 7 Finance leases 1 Weighted average discount rates Operating leases 4.6 % Finance leases 5.0 %

Stock-based Compensation (Table

Stock-based Compensation (Tables)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 2019 and 2018 : Three Months Ended Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands) Cost of revenues $ 552 $ 609 $ 1,097 $ 1,263 Research and development 2,704 1,976 5,044 3,817 Sales and marketing 1,063 1,105 2,131 2,506 General and administrative 4,016 3,333 8,508 8,328 Total stock-based compensation $ 8,335 $ 7,023 $ 16,780 $ 15,914
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 191,875 $ 91.13 Exercised (344,851 ) $ 26.07 Canceled (90,932 ) $ 66.12 Balance as of June 30, 2019 3,185,401 $ 35.00 6.2 $ 167,275 Vested and expected to vest - June 30, 2019 3,021,949 $ 33.04 6.0 $ 164,336 Exercisable - June 30, 2019 2,399,078 $ 26.85 5.5 $ 144,641
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 194,944 $ 82.33 Vested (226,355 ) $ 53.35 Canceled (91,429 ) $ 62.26 Balance as of June 30, 2019 1,104,043 $ 60.38 Outstanding and expected to vest - June 30, 2019 822,916 $ 59.03

Net Income Per Share (Tables)

Net Income Per Share (Tables)	6 Months Ended
	Jun. 30, 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 Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands, except per share data) Numerator: Net income $ 16,232 $ 10,293 $ 29,498 $ 19,435 Denominator: Weighted-average shares used in computing net income per share: Basic 39,198 38,987 39,143 38,843 Effect of potentially dilutive securities: Common stock options 1,890 2,610 1,950 2,576 Restricted stock units 442 618 477 655 Diluted 41,530 42,215 41,570 42,074 Net income per share: Basic $ 0.41 $ 0.26 $ 0.75 $ 0.50 Diluted $ 0.39 $ 0.24 $ 0.71 $ 0.46
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 Six Months Ended June 30, June 30, 2019 2018 2019 2018 (in thousands) Common stock options 419 125 381 81 Restricted stock units 54 2 62 30 473 127 443 111

Segment Information and Infor_2

Segment Information and Information about Geographic Area (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Revenues be geographic area	Revenues by sales channel are as follows (in thousands): Three Months Ended Six Months Ended June 30, June 30, 2019 2018 2019 2018 Direct $ 45,672 $ 35,294 $ 88,711 $ 74,004 Partner 33,257 32,859 65,561 59,027 Total $ 78,929 $ 68,153 $ 154,272 $ 133,031
Revenues and property and equipment, net, by geographic area	ds): Three Months Ended Six Months Ended June 30, June 30, 2019 2018 2019 2018 United States $ 50,704 $ 45,799 $ 99,325 $ 90,113 Foreign 28,225 22,354 54,947 42,918 Total $ 78,929 $ 68,153 $ 154,272 $ 133,031

The Company and Summary of Si_3

The Company and Summary of Significant Accounting Policies (Details) £ in Millions	Dec. 31, 2018USD ($)	Jun. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2019GBP (£)	Jun. 30, 2019USD ($)	Jan. 01, 2019USD ($)
Reclassification
Operating Lease, Right-of-Use Asset						$ 28,101,000
Share-based Compensation		$ 200,000		$ 500,000
Capitalization of internally developed software costs		$ 200,000		$ 400,000
Capitalized Computer Software, Unamortized	$ 1,200,000					1,600,000
Amortization expense for capitalized internally developed software			$ 100,000
Investment in privately held company			2,500,000
Retained earnings	27,964,000					36,682,000
Restricted cash	1,200,000		$ 1,200,000			1,200,000
Operating Lease, Liability						38,813,000
Capitalized Computer Software, Amortization Period				3 years
Advance Royalties						$ 600,000
Tenant Improvement Allowance	$ 6,900,000
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)
Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | Foreign Currency Contract, Euro [Member]
Reclassification
Derivative, notional amount | £					£ 18.9
Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | Foreign Currency Contract, Pound [Member]
Reclassification
Derivative, notional amount | £					£ 9.2

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Cash and Cash Equivalents, Available-for-sale Securities Reconciliation (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	$ 91,381
Unrealized Gains	1,181	$ 22
Unrealized (Losses)	(48)	(567)
Fair Value	410,528	365,876
Debt Securities, Available-for-sale, Amortized Cost	409,395	366,421
Cash and cash equivalents:
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		41,026
Current Assets [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	226	9
Unrealized (Losses)	(48)	(193)
Fair Value	207,626	248,140
Debt Securities, Available-for-sale, Amortized Cost	207,448	248,324
Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	955	13
Unrealized (Losses)	0	(374)
Fair Value	111,521	76,710
Debt Securities, Available-for-sale, Amortized Cost	110,566	77,071
Asset backed securities | Current Assets [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	1	0
Unrealized (Losses)	(1)	(15)
Fair Value	8,840	10,432
Debt Securities, Available-for-sale, Amortized Cost	8,840	10,447
Asset backed securities | Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	244	10
Unrealized (Losses)	0	(28)
Fair Value	41,077	22,927
Debt Securities, Available-for-sale, Amortized Cost	40,833	22,945
Commercial paper | Cash and cash equivalents:
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	500
Available-for-sale Securities, Amortized Cost Basis	500
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0
Commercial paper | Current Assets [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains		0
Unrealized (Losses)		0
Fair Value		3,237
Debt Securities, Available-for-sale, Amortized Cost		3,237
Corporate bonds | Current Assets [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	46	0
Unrealized (Losses)	(39)	(84)
Fair Value	36,259	30,822
Debt Securities, Available-for-sale, Amortized Cost	36,252	30,906
Corporate bonds | Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	228	3
Unrealized (Losses)	0	(293)
Fair Value	25,610	35,032
Debt Securities, Available-for-sale, Amortized Cost	25,382	35,322
US government agencies | Current Assets [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	179	9
Unrealized (Losses)	(8)	(94)
Fair Value	162,527	203,649
Debt Securities, Available-for-sale, Amortized Cost	162,356	203,734
US government agencies | Long-term investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Unrealized Gains	483	0
Unrealized (Losses)	0	(53)
Fair Value	44,834	18,751
Debt Securities, Available-for-sale, Amortized Cost	44,351	18,804
Cash Equivalents [Member] | Money market funds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	727	113
Cash [Member]
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	$ 90,154	$ 40,913

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		9 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 373,403	$ 357,989	$ 366,319	$ 343,544	$ 357,989	$ 343,544	$ 343,544
Change in net unrealized gain, net of tax	739		144		1,422	(247)
Amounts reclassified for net realized gain included in net income	15		79		43	95
Other comprehensive income (loss), net	930	896	144	(391)	1,826	(247)
Ending balance	$ 383,598	$ 373,403	$ 365,239	366,319	$ 383,598	365,239
Unrealized Gain (Loss) on Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance				$ (545)		$ (545)	(545)
Change in net unrealized gain, net of tax							1,379
Amounts reclassified for net realized gain included in net income							43
Other comprehensive income (loss), net							1,422
Ending balance							$ 877

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	$ 319,647
Level 1 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		$ 0	$ 0
Level 2 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		319,647	324,850
Level 3 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0	0
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	500
Commercial paper | Level 1 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
Debt Securities, Available-for-sale			0
Commercial paper | Level 2 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	500
Debt Securities, Available-for-sale			3,237
Commercial paper | Level 3 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0
Debt Securities, Available-for-sale			0
US government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	207,361
US government agencies | Level 1 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0		0
US government agencies | Level 2 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	207,361		222,400
US government agencies | Level 3 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0		0
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	61,869
Corporate bonds | Level 1 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0		0
Corporate bonds | Level 2 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	61,869		65,854
Corporate bonds | Level 3 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0		0
Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	49,917
Asset backed securities | Level 1 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	0		0
Asset backed securities | Level 2 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	49,917		33,359
Asset backed securities | Level 3 | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	$ 0		0
Fair Value | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		319,647	324,850
Fair Value | Commercial paper | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		500
Debt Securities, Available-for-sale			3,237
Fair Value | US government agencies | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		207,361	222,400
Fair Value | Corporate bonds | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		61,869	65,854
Fair Value | Asset backed securities | Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		$ 49,917	$ 33,359

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Contractual Maturity (Details) $ in Thousands	Dec. 31, 2018USD ($)
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Debt and Equity Maturities, Next Twelve Months, Fair Value	$ 229,614
Available-for-sale Securities, Debt and Equity Maturities, Year One through Two, Fair Value	64,521
Available-for-sale Securities, Debt and Equity Maturities, After Year Two, Fair Value	25,512
Debt Securities, Available-for-sale	319,647
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Debt and Equity Maturities, Next Twelve Months, Fair Value	500
Available-for-sale Securities, Debt and Equity Maturities, Year One through Two, Fair Value	0
Available-for-sale Securities, Debt and Equity Maturities, After Year Two, Fair Value	0
US government agencies
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Debt and Equity Maturities, Next Twelve Months, Fair Value	162,527
Available-for-sale Securities, Debt and Equity Maturities, Year One through Two, Fair Value	30,192
Available-for-sale Securities, Debt and Equity Maturities, After Year Two, Fair Value	14,642
Debt Securities, Available-for-sale	207,361
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Debt and Equity Maturities, Next Twelve Months, Fair Value	36,258
Available-for-sale Securities, Debt and Equity Maturities, Year One through Two, Fair Value	19,651
Available-for-sale Securities, Debt and Equity Maturities, After Year Two, Fair Value	5,960
Debt Securities, Available-for-sale	61,869
Asset backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Debt and Equity Maturities, Next Twelve Months, Fair Value	30,329
Available-for-sale Securities, Debt and Equity Maturities, Year One through Two, Fair Value	14,678
Available-for-sale Securities, Debt and Equity Maturities, After Year Two, Fair Value	4,910
Debt Securities, Available-for-sale	$ 49,917

Fair Value of Financial Instr_7

Fair Value of Financial Instruments - Derivatives (Details) € in Millions, £ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019GBP (£)contract	Dec. 31, 2018GBP (£)contract	Dec. 31, 2018EUR (€)contract	Sep. 30, 2018contract	Dec. 31, 2017USD ($)contract
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax | $	$ 200,000	$ 200,000	$ 400,000	$ 400,000
Foreign currency contract, asset, fair value disclosure | $									$ 0
Forward Contracts
Derivatives, Fair Value [Line Items]
Derivative, number of instruments held | contract						2	2	5	2
Derivative, notional amount						£ 4.1	€ 12.9
Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative, number of instruments held | contract					26
Not Designated as Hedging Instrument [Member] | Foreign Currency Contract, Euro [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount					£ 10	16
Not Designated as Hedging Instrument [Member] | Foreign Currency Contract, Pound [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount					4	£ 6.3
Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | Foreign Currency Contract, Euro [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount					18.9
Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | Foreign Currency Contract, Pound [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount					£ 9.2

Fair Value of Financial Instr_8

Fair Value of Financial Instruments - Gains (Losses) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Other foreign currency transactions gain (loss)	$ 249	$ (1,357)	$ 55	$ (549)
Total foreign exchange gain (loss), net	293	(467)	133	(235)
Forward Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) from forward contracts	$ 44	$ 890	$ 78	$ 314

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 170,942					$ 160,672
Finance leases - right of use asset			$ 1,883
Less: accumulated depreciation and amortization	(111,583)					(99,230)
Property and equipment, net	59,359		59,359		$ 61,442	61,442
Depreciation and amortization expense	6,300	$ 6,400	$ 12,700	$ 12,800
Capital leases, accumulated depreciation	1,600
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	102,868					93,530
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	26,788					26,030
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	5,966					5,814
Finance leases - right of use asset
Property, Plant and Equipment [Line Items]
Finance leases - right of use asset	3,503					3,503
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	15,349					15,356
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net					7,900	6,000
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment					$ 1,800	900
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 16,468					$ 16,439

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		9 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Capitalized Contract Cost, Amortization Period	5 years				5 years
Retained earnings	$ 36,682				$ 36,682			$ 27,964
Amortization of commissions assets		$ 500			900	$ 500	$ 300
Revenue recognized	78,929	78,929	$ 68,153	$ 68,153	$ 154,272	$ 133,031
Subscription Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized	$ 49,100	$ 113,300	$ 42,800	$ 98,400

Revenue from Contracts with C_4

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	$ 1,958	$ 1,480
Commission asset, noncurrent	$ 5,662	$ 4,692

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Allowance for doubtful accounts receivable	$ (648)	$ (683)
Total accounts receivable, net	$ 63,184	$ 75,825

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Unbilled contracts (Details) $ in Thousands	Sep. 30, 2018USD ($)
Revenue from Contract with Customer [Abstract]
Contracts expected to be billed remainder of year	$ 36,395
Unbilled Receivables, Expected To Be Billed In 2019	46,266
Unbilled Receivables, Expected To Be Billed In 2020	20,830
Unbilled Receivables, Expected To Be Billed In 2021	4,230
Unbilled Receivables, Expected To Be Billed In 2022	1,150
Unbilled Receivables, Expected To Be Billed Thereafter	268
Revenue, Remaining Performance Obligation, Amount	$ 109,139

Revenue from Contracts with C_7

Revenue from Contracts with Customers - Revenue by sales channel (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 78,929	$ 78,929	$ 68,153	$ 68,153	$ 154,272	$ 133,031
Direct
Disaggregation of Revenue [Line Items]
Revenues		45,672		35,294	88,711	74,004
Partner
Disaggregation of Revenue [Line Items]
Revenues		$ 33,257		$ 32,859	$ 65,561	$ 59,027

Business Combination - Narrativ

Business Combination - Narrative (Details) - USD ($) $ in Thousands	Jan. 10, 2019	Apr. 01, 2018	Jun. 30, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill			$ 7,325	$ 7,225
1Mobility
Business Acquisition [Line Items]
Total purchase price	$ 200			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
Developed Technology [Member]
Business Acquisition [Line Items]
Estimated useful life of technology-based intangible assets			4 years

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets, Net - Carrying Value of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Schedule of Goodwill and Intangible Assets [Line Items]
Cost	$ 27,743				$ 27,743			$ 26,843
Accumulated Amortization	(7,947)				(7,947)			(4,907)
Net Book Value	19,796				19,796			21,936
Intangible assets not subject to amortization	40				40			40
Total intangible assets, net	19,836		$ 19,836		$ 19,836		$ 21,976	21,976
Amortization of intangible assets	1,500	$ 900	3,000	$ 1,500
Goodwill			$ 7,325				$ 7,225
Developed technology
Schedule of Goodwill and Intangible Assets [Line Items]
Weighted Average Life (Years)					5 years
Weighted Average Remaining Life (Years)					3 years 2 months 12 days	3 years 9 months 18 days
Cost	26,356				$ 26,356			25,456
Accumulated Amortization	(7,076)				(7,076)			(4,085)
Net Book Value	19,280				$ 19,280			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 2 months 12 days	5 years 10 months 24 days
Cost	1,387				$ 1,387			1,387
Accumulated Amortization	(871)				(871)			(822)
Net Book Value	$ 516				$ 516			$ 565

Goodwill and Intangible Asset_4

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 six months)	$ 3,041
2018	6,081
2019	6,081
2020	4,427
2021	100
2024 and thereafter	66
Net Book Value	$ 19,796	$ 21,936

Leases (Details)

Leases (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Sep. 30, 2018	Jan. 01, 2018
Lessee, Lease, Description [Line Items]
Arrangement interest rate	5.00%
Lease, Expense		$ 2,000,000	$ 1,300,000	$ 3,600,000	$ 2,500,000
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year							$ 4,502,000
Operating Lease, Right-of-Use Asset		$ 28,101,000		$ 28,101,000
Operating Lease, Weighted Average Remaining Lease Term		7 years		7 years
Finance Lease, Weighted Average Remaining Lease Term		1 year		1 year
Operating Lease, Weighted Average Discount Rate, Percent		4.60%		4.60%
Finance Lease, Weighted Average Discount Rate, Percent		5.00%		5.00%
Finance leases - right of use asset		$ 1,883,000		$ 1,883,000
Lease, Right-of-Use Asset		29,984,000		29,984,000
Operating Lease, Liability, Current		(6,826,000)		(6,826,000)		$ 0
Finance Lease, Liability, Current		(741,000)		(741,000)
Operating Lease, Liability, Noncurrent		31,987,000		31,987,000
Finance Lease, Liability, Noncurrent		117,000		117,000
Lease, Liability		39,671,000		39,671,000
Finance Lease, Liability, Payments, Remainder of Fiscal Year		885,000		885,000
Lessee, Operating Lease, Liability, Payments, Due Year Two							7,845,000
Finance Lease, Liability, Payments, Due Year Two		130,000		130,000
Lessee, Operating Lease, Liability, Payments, Due Year Three							6,137,000
Finance Lease, Liability, Payments, Due Year Three		54,000		54,000
Lessee, Operating Lease, Liability, Payments, Due Year Four							4,544,000
Finance Lease, Liability, Payments, Due Year Four		0		0
Lessee, Operating Lease, Liability, Payments, Due Year Five							4,299,000
Finance Lease, Liability, Payments, Due Year Five		0		0
Lessee, Operating Lease, Liability, Payments, Due after Year Five							19,299,000
Finance Lease, Liability, Payments, Due after Year Five		0		0
Lessee, Operating Lease, Liability, Payments, Due							$ 46,626,000
Finance Lease, Liability, Payments, Due		1,069,000		1,069,000
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		7,813,000		7,813,000
Finance Lease, Liability, Undiscounted Excess Amount		211,000		211,000
Operating Lease, Liability		38,813,000		38,813,000
Finance Lease, Liability		858,000		858,000				$ 3,500,000
Accrued Liabilities [Member]
Lessee, Lease, Description [Line Items]
Finance Lease, Liability, Current		$ (741,000)		$ (741,000)

Commitments and Contingencies

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 - Sto

Stock-based Compensation - Stock Options (Details) - shares	Jun. 30, 2019	Sep. 30, 2018
2012 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	11,800,000
Number of shares available for grant	5,600,000
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 - Exp

Stock-based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	$ 8,335	$ 7,023	$ 16,780	$ 15,914
Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized employee compensation cost	13,200		$ 13,200
Unrecognized employee compensation cost, period for recognition			2 years 2 months 12 days
Restricted Stock Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized employee compensation cost	50,700		$ 50,700
Unrecognized employee compensation cost, period for recognition			2 years 6 months
Cost of revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	552	609			$ 1,097	$ 1,263
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	2,704	1,976			5,044	3,817
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	1,063	1,105			2,131	2,506
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	$ 4,016	$ 3,333			$ 8,508	$ 8,328

Stock-based Compensation - S_2

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)	191,875
Exercised (in shares)	(344,851)
Canceled (in shares)	(90,932)
Ending balance (in shares)	3,185,401
Vested and expected to vest (in shares)	3,021,949
Exercisable (in shares)	2,399,078
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)	91.13
Weighted average exercise price, exercised (in dollars per share)	26.07
Weighted average exercise price, canceled (in dollars per share)	66.12
Weighted average exercise price, Ending balance (in dollars per share)	35
Weighted average exercise price, Vested and expected to vest (in dollars per share)	33.04
Weighted average exercise price, Exercisable (in dollars per share)	$ 26.85
Weighted Average Remaining Contractual Life
Weighted average remaining contractual life (in years)	6 years 2 months 12 days	6 years 4 months 24 days
Weighted Average Remaining Contractual Life (Years), Vested and Expected to Vest	6 years
Weighted Average Remaining Contractual Life (Years), Exercisable	5 years 6 months
Aggregate Intrinsic Value
Aggregate intrinsic value	$ 167,275		$ 149,935
Aggregate intrinsic value, Vested and expected to vest	164,336
Aggregate intrinsic value, Exercisable	$ 144,641

Stock-based Compensation - Res

Stock-based Compensation - Restricted Stock (Details) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Outstanding RSUs
Beginning balance (in shares) | shares	1,226,883
Granted (in shares) | shares	194,944
Released (in shares) | shares	(226,355)
Canceled (in shares) | shares	(91,429)
Ending balance (in shares) | shares	1,104,043
Outstanding and expected to vest (in shares) | shares	822,916
Weighted Average Fair Value
Beginning balance (usd per share) | $ / shares	$ 55.71
Granted (usd per share) | $ / shares	82.33
Released (usd per share) | $ / shares	53.35
Canceled (usd per share) | $ / shares	62.26
Ending balance (usd per share) | $ / shares	60.38
Outstanding and expected to vest (usd per share) | $ / shares	$ 59.03

Net Income Per Share (Details)

Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income	$ 16,232	$ 13,266		$ 10,293	$ 9,142		$ 29,498	$ 19,435	$ 29,498	$ 19,435
Denominator:
Basic (shares)	39,198			38,987			39,143	38,843	39,143	38,843
Common stock options (shares)			1,890			2,610			1,950	2,576
Restricted stock units (shares)			442			618			477	655
Diluted (shares)	41,530			42,215			41,570	42,074	41,570	42,074
Basic (USD per share)	$ 0.41			$ 0.26			$ 0.75	$ 0.50	$ 0.75	$ 0.50
Diluted (USD per share)	$ 0.39			$ 0.24			$ 0.71	$ 0.46	$ 0.71	$ 0.46
Antidilutive Securities
Antidilutive securities (shares)			473			127			443	111
Stock Options
Antidilutive Securities
Antidilutive securities (shares)			419			125			381	81
Restricted Stock Units
Antidilutive Securities
Antidilutive securities (shares)			54			2			62	30

Stockholder's Equity (Details)

Stockholder's Equity (Details) - USD ($)	3 Months Ended
	Sep. 30, 2018	Oct. 30, 2018	Feb. 05, 2018
Equity [Abstract]
Share repurchase program, authorized amount		$ 100,000,000	$ 100,000,000
Shares repurchased during period (in shares)	278,038
Shares repurchased during period, value	$ 24,100,000
Remaining authorized amount	$ 90,800,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 2,277		$ 1,486		$ 4,848	$ 1,995
Effective tax rate		12.30%		12.60%
Unrecognized Tax Benefits		$ 7,400					$ 6,400
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 4,100					$ 3,500

Segment Information and Infor_3

Segment Information and Information about Geographic Area - Revenue by geographic area (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 78,929	$ 78,929	$ 68,153	$ 68,153	$ 154,272	$ 133,031
United States
Disaggregation of Revenue [Line Items]
Revenues	50,704		45,799		99,325	90,113
Foreign
Disaggregation of Revenue [Line Items]
Revenues	$ 28,225		$ 22,354		$ 54,947	$ 42,918

Segment Information and Infor_4

Segment Information and Information about Geographic Area - Property and Equipment, net (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)segment	Jun. 30, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of operating segments (in segment) | segment	1
Property and equipment, net	$ 59,359	$ 59,359	$ 61,442	$ 61,442
United States
Segment Reporting Information [Line Items]
Property and equipment, net		56,511	59,222
Other
Segment Reporting Information [Line Items]
Property and equipment, net		$ 2,848	$ 2,220

Uncategorized Items - qlys-2019

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