The Company and Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2020
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 IT, 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, 2019, 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 months ended March 31, 2020 are not necessarily indicative of the results of operations expected for the entire year ending December 31, 2020 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, 2019, filed with the SEC on February 21, 2020. Risks and Uncertainties In March 2020, the World Health Organization declared the outbreak of a novel strain of coronavirus (“COVID-19”) as a pandemic. As a result of COVID-19, the Company has modified certain aspects of our business, including restricting employee travel, requiring employees to work from home, and canceling certain events and meetings, among other modifications. The Company will continue to actively monitor the situation and may take further actions that alter its business operations as may be required by federal, state or local authorities or that the Company determines are in the best interests of its employees, customers, partners, suppliers and stockholders. While the Company has not incurred significant disruptions from the COVID-19 outbreak, the Company is unable to accurately predict the full impact that COVID-19 will have due to numerous uncertainties, including the duration of the outbreak, actions that may be taken by governmental authorities and the impact to the business of its customers and partners. The Company will continue to evaluate the nature and extent of the impact to its business, financial position, results of operations and cash flows. 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 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 net asset positions, to date primarily cash, accounts receivable and operating lease liabilities (non-designated forward contracts), as well as to manage foreign currency fluctuation risk related to forecasted transactions (designated cash flow hedges). Open contracts are recorded within prepaid expenses and other current assets, other noncurrent assets, accrued liabilities or other noncurrent 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 recorded within accumulated other comprehensive income ("AOCI") and then reclassified to revenue or operating expenses when the hedged item impacts the condensed consolidated statements of operations. Stock-Based Compensation The Company recognizes the fair value of its employee stock options and restricted stock units over the requisite service periods for those awards ultimately expected to vest. The fair value of each option is estimated on the date of grant using the Black-Scholes-Merton option pricing model and the fair value of each restricted stock unit ("RSU") is based on the price 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 stock options, and accounts for these awards and options 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 there are any changes in the probability of achievement, the Company recognizes the cumulative effect in the period when the estimate changes. Non-marketable securities During the fiscal year ended December 31, 2018, the Company invested $2.5 million in preferred stock of a privately-held company. The fair value of the investment is not readily available, and there are no quoted market prices for the investment. The investment is included in other noncurrent assets on the consolidated balance sheets and measured at cost less impairment, adjusted for observable price changes. The investment is assessed for impairment annually or whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. As of March 31, 2020 and December 31, 2019, no impairment was recorded for the investment. During the second quarter 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. During the third quarter ended September 30, 2019, the Company made an additional investment of $0.6 million in a convertible security issued by this investee and recorded it in other current assets on the condensed consolidated balance sheet. Recently Adopted Accounting Pronouncements
Recently adopted Accounting Pronouncements and Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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. It also requires the Company to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement. The Company adopted this ASU prospectively to applicable implementation costs incurred since January 1, 2020. Applicable implementation costs capitalized during the three months ended March 31, 2020 were not material. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326) as modified by subsequently issued ASU No. 2018-19, 2019-04 and 2019-05, which introduces a new accounting model, Current Expected Credit Losses (CECL). CECL requires earlier recognition of credit losses, while also providing additional transparency about credit risk. CECL utilizes a lifetime expected credit loss measurement objective for the recognition of credit losses at the time the financial asset is originated or acquired. The expected credit losses are adjusted each period for changes in expected lifetime credit losses. The Company adopted this ASU on January 1, 2020, using a modified retrospective transition method, which requires a cumulative-effect adjustment, if any, to the opening balance of retained earnings to be recognized on the date of adoption with prior periods not restated. The adoption did not have a material impact on the Company's consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In January 2020, the FASB issued ASU No. 2020-01, Investments—Equity Securities (Topic 321), Investments—Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815) (ASU 2020-01). This ASU clarifies the interaction of the accounting for equity securities under Topic 321, the accounting for equity method investments in Topic 323, and the accounting for certain forward contracts and purchased options in Topic 815. It is effective for the Company beginning in the first quarter of fiscal 2021, and earlier adoption is permitted. The Company is currently evaluating the impact of its pending adoption of ASU 2020-01 on the Company's consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes, eliminates certain exceptions within ASC 740, Income Taxes, and clarifies certain aspects of the current guidance to promote consistency among reporting entities. ASU 2019-12 is effective for the Company for fiscal years beginning after December 15, 2020. Most amendments within the standard are required to be applied on a prospective basis, while certain amendments must be applied on a retrospective or modified retrospective basis. The Company is currently evaluating the impacts of the provisions of ASU 2019-12 on its consolidated financial statements.
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 Level 1 assets include a highly liquid money market funds, which are valued using unadjusted quoted prices that are available in an active market for an identical asset. Level 2 assets include fixed-income U.S. government agency securities, commercial paper, corporate bonds, asset-backed securities and derivative financial instruments consisting of foreign currency forward contracts. The securities, bonds and commercial paper are valued using prices from independent pricing services based on quoted prices in active markets for similar instruments or on industry models using data inputs such as interest rates and prices that can be directly observed or corroborated in active markets. The foreign currency forward contracts are valued using observable inputs, such as quotations on forward foreign exchange points and foreign interest rates. During the fiscal year ended December 31, 2019 and 2018, the Company made investments of $0.6 million in a convertible security and $2.5 million in preferred stock, respectively, issued by a privately-held company. The estimated fair value of the investments was determined based on Level 3 inputs. As of March 31, 2020 and December 31, 2019, management estimated that the fair value of the investments equaled their carrying value.

The Company and Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2020

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 IT, 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, 2019, 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 months ended March 31, 2020 are not necessarily indicative of the results of operations expected for the entire year ending December 31, 2020 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, 2019, filed with the SEC on February 21, 2020.

Risks and Uncertainties

In March 2020, the World Health Organization declared the outbreak of a novel strain of coronavirus (“COVID-19”) as a pandemic. As a result of COVID-19, the Company has modified certain aspects of our business, including restricting employee travel, requiring employees to work from home, and canceling certain events and meetings, among other modifications. The Company will continue to actively monitor the situation and may take further actions that alter its business operations as may be required by federal, state or local authorities or that the Company determines are in the best interests of its employees, customers, partners, suppliers and stockholders. While the Company has not incurred significant disruptions from the COVID-19 outbreak, the Company is unable to accurately predict the full impact that COVID-19 will have due to numerous uncertainties, including the duration of the outbreak, actions that may be taken by governmental authorities and the impact to the business of its customers and partners. The Company will continue to evaluate the nature and extent of the impact to its business, financial position, results of operations and cash flows.

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 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 net asset positions, to date primarily cash, accounts receivable and operating lease liabilities (non-designated forward contracts), as well as to manage foreign currency fluctuation risk related to forecasted transactions (designated cash flow hedges). Open contracts are recorded within prepaid expenses and other current assets, other noncurrent assets, accrued liabilities or other noncurrent 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 recorded within accumulated other comprehensive income ("AOCI") and then reclassified to revenue or operating expenses when the hedged item impacts the condensed consolidated statements of operations.

Stock-Based Compensation

The Company recognizes the fair value of its employee stock options and restricted stock units over the requisite service periods for those awards ultimately expected to vest. The fair value of each option is estimated on the date of grant using the Black-Scholes-Merton option pricing model and the fair value of each restricted stock unit ("RSU") is based on the price 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 stock options, and accounts for these awards and options 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 there are any changes in the probability of achievement, the Company recognizes the cumulative effect in the period when the estimate changes.

Non-marketable securities

During the fiscal year ended December 31, 2018, the Company invested $2.5 million in preferred stock of a privately-held company. The fair value of the investment is not readily available, and there are no quoted market prices for the investment. The investment is included in other noncurrent assets on the consolidated balance sheets and measured at cost less impairment, adjusted for observable price changes. The investment is assessed for impairment annually or whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. As of March 31, 2020 and December 31, 2019, no impairment was recorded for the investment. During the second quarter 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. During the third quarter ended September 30, 2019, the Company made an additional investment of $0.6 million in a convertible security issued by this investee and recorded it in other current assets on the condensed consolidated balance sheet.

Recently Adopted Accounting Pronouncements

Recently adopted Accounting Pronouncements and Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

In August 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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. It also requires the Company to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement. The Company adopted this ASU prospectively to applicable implementation costs incurred since January 1, 2020. Applicable implementation costs capitalized during the three months ended March 31, 2020 were not material.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326) as modified by subsequently issued ASU No. 2018-19, 2019-04 and 2019-05, which introduces a new accounting model, Current

Expected Credit Losses (CECL). CECL requires earlier recognition of credit losses, while also providing additional transparency about credit risk. CECL utilizes a lifetime expected credit loss measurement objective for the recognition of credit losses at the time the financial asset is originated or acquired. The expected credit losses are adjusted each period for changes in expected lifetime credit losses. The Company adopted this ASU on January 1, 2020, using a modified retrospective transition method, which requires a cumulative-effect adjustment, if any, to the opening balance of retained earnings to be recognized on the date of adoption with prior periods not restated. The adoption did not have a material impact on the Company's consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Adopted

In January 2020, the FASB issued ASU No. 2020-01, Investments—Equity Securities (Topic 321), Investments—Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815) (ASU 2020-01). This ASU clarifies the interaction of the accounting for equity securities under Topic 321, the accounting for equity method investments in Topic 323, and the accounting for certain forward contracts and purchased options in Topic 815. It is effective for the Company beginning in the first quarter of fiscal 2021, and earlier adoption is permitted. The Company is currently evaluating the impact of its pending adoption of ASU 2020-01 on the Company's consolidated financial statements.

In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (ASU 2019-12), which simplifies the accounting for income taxes, eliminates certain exceptions within ASC 740, Income Taxes, and clarifies certain aspects of the current guidance to promote consistency among reporting entities. ASU 2019-12 is effective for the Company for fiscal years beginning after December 15, 2020. Most amendments within the standard are required to be applied on a prospective basis, while certain amendments must be applied on a retrospective or modified retrospective basis. The Company is currently evaluating the impacts of the provisions of ASU 2019-12 on its consolidated financial statements.

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 Level 1 assets include a highly liquid money market funds, which are valued using unadjusted quoted prices that are available in an active market for an identical asset. Level 2 assets include fixed-income U.S. government agency securities, commercial paper, corporate bonds, asset-backed securities and derivative financial instruments consisting of foreign currency forward contracts. The securities, bonds and commercial paper are valued using prices from independent pricing services based on quoted prices in active markets for similar instruments or on industry models using data inputs such as interest rates and prices that can be directly observed or corroborated in active markets. The foreign currency forward contracts are valued using observable inputs, such as quotations on forward foreign exchange points and foreign interest rates. During the fiscal year ended December 31, 2019 and 2018, the Company made investments of $0.6 million in a convertible security and $2.5 million in preferred stock, respectively, issued by a privately-held company. The estimated fair value of the investments was determined based on Level 3 inputs. As of March 31, 2020 and December 31, 2019, management estimated that the fair value of the investments equaled their carrying value.