Document and Entity Information Document Information [Table] Document Information [Line Items] Document Type Document Quarterly Report Document Period End Date Document Transition Report Entity File Number Entity Registrant Name Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Address, Address Line One Entity Address, City or Town Entity Address, State or Province Entity Address, Postal Zip Code City Area Code Local Phone Number Title of 12(b) Security Trading Symbol Security Exchange Name Entity Current Reporting Status Entity Interactive Data Current Entity Filer Category Entity Small Business Entity Emerging Growth Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Central Index Key Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Period Focus Amendment Flag Consolidated Balance Sheets Statement [Table] Statement [Line Items] Statement Assets [Abstract] Assets Assets, Current [Abstract] Current assets: Cash and cash equivalents Fair value of cash and cash equivalents Cash and cash equivalents Debt Securities, Available-for-sale, Current Corporate investments Accounts Receivable, Net, Current Accounts receivable, net Capitalized Contract Cost, Net, Current Deferred contract costs Prepaid Expense and Other Assets, Current Prepaid expenses and other Represents the sum of the carrying amounts as of the balance sheet date of all assets, before funds held for clients, that are expected to be realized in cash, sold, or consumed within one year (or the normal operating cycle, if longer). Assets Current before Funds Held for Clients Total current assets before funds held for clients Funds Held for Clients Funds held for clients Assets, Current Total current assets Capitalized Computer Software, Net Capitalized internal-use software, net Capitalized internal-use software, net Property, Plant and Equipment, Net Property and equipment, net Property and equipment, net Operating Lease, Right-of-Use Asset Operating lease right-of-use assets Finite-Lived Intangible Assets, Net Intangible assets, net Intangible assets, net Goodwill Capitalized Contract Cost, Net, Noncurrent Long-term deferred contract costs Prepaid Expense and Other Assets, Noncurrent Long-term prepaid expenses and other Deferred Income Tax Assets, Net Deferred income tax assets Assets Total assets Liabilities and Equity [Abstract] Liabilities and Stockholders' Equity Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Accrued Liabilities, Current Accrued expenses Total accrued expenses Represents the amount of total current liabilities, before client fund obligations, incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer. Liabilities Current before Client Fund Obligations Total current liabilities before client fund obligations Represents the amount of obligations related to client funds that will be paid within the next twelve months or within one business cycle, if longer. Client Fund Obligations Current Client fund obligations Liabilities, Current Total current liabilities Deferred Rent Credit, Noncurrent Deferred rent Operating Lease, Liability, Noncurrent Long-term operating lease liabilities Other Liabilities, Noncurrent Other long-term liabilities Deferred Income Tax Liabilities, Net Deferred income tax liabilities Liabilities Total liabilities Stockholders' Equity Attributable to Parent [Abstract] Stockholders' equity: Preferred Stock, Value, Issued Preferred stock, $0.001 par value, 5,000 authorized, no shares issued and outstanding at June 30, 2019 and December 31, 2019 Common Stock, Value, Issued Common stock, $0.001 par value, 155,000 shares authorized at June 30, 2019 and December 31, 2019; 53,075 shares issued and outstanding at June 30, 2019 and 53,573 shares issued and outstanding at December 31, 2019 Additional Paid in Capital Additional paid-in capital Retained Earnings (Accumulated Deficit) Retained earnings Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income Stockholders' Equity Attributable to Parent Balance Balance Total stockholders' equity Liabilities and Equity Total liabilities and stockholders' equity Preferred Stock, Par or Stated Value Per Share Preferred Stock, par value (in dollars per share) Preferred Stock, Shares Authorized Preferred Stock, shares authorized Preferred Stock, Shares Issued Preferred Stock, shares issued Preferred Stock, Shares Outstanding Preferred Stock, shares outstanding Common Stock, Par or Stated Value Per Share Common Stock, par value (in dollars per share) Common Stock, Shares Authorized Common Stock, shares authorized Common Stock, Shares, Issued Common Stock, shares issued Common Stock, Shares, Outstanding Balance (in shares) Balance (in shares) Common Stock, shares outstanding Consolidated Statements of Operations and Comprehensive Income Revenues [Abstract] Revenues: Revenue from Contract with Customer, Excluding Assessed Tax Recurring and other revenue Revenue Not from Contract with Customer Interest income on funds held for clients Revenues Total revenues Cost of Goods and Services Sold [Abstract] Cost of revenues: Cost of Services Cost of revenues Gross Profit Gross profit Operating Expenses [Abstract] Operating expenses: Selling and Marketing Expense Sales and marketing Research and Development Expense Research and development General and Administrative Expense General and administrative Operating Expenses Total operating expenses Operating Income (Loss) Operating income Nonoperating Income (Expense) Other income Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income before income taxes Income Tax Expense (Benefit) Income tax expense (benefit) Net Income (Loss) Attributable to Parent Net income Net income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive loss, net of tax Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Unrealized losses on securities, net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Total other comprehensive loss, net of tax Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income Earnings Per Share, Basic and Diluted [Abstract] Net income per share: Earnings Per Share, Basic Basic (in dollars per share) Earnings Per Share, Diluted Diluted (in dollars per share) Weighted-average shares used in computing net loss per share attributable to common stockholders: Weighted-average shares used in computing net income per share: Weighted Average Number of Shares Outstanding, Basic Basic (in shares) Weighted Average Number of Shares Outstanding, Diluted Diluted (in shares) Diluted (in shares) Consolidated Statement of Changes in Stockholders' Equity Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Common Stock Additional Paid In Capital [Member] Additional Paid-in Capital Retained Earnings [Member] Retained Earnings (Accumulated Deficit). Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income (Loss) Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Cumulative Effect of New Accounting Principle in Period of Adoption Cumulative effect of change in accounting policy (adoption of Topic 606) Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock-based compensation Stock Issued During Period, Value, Stock Options Exercised Stock options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Options exercised Stock options exercised (in shares) Represents the aggregate change in value due to restricted stock units that vested during the period. Adjustments to Additional Paid in Capital Restricted Stock Vesting Issuance of common stock upon vesting of restricted stock units Represents the number of shares of stock related to restricted stock units that vested during the period. Stock Issued During Period Shares Restricted Stock Units Vesting Issuance of common stock upon vesting of restricted stock units (in shares) Stock Issued During Period, Value, Employee Stock Purchase Plan Issuance of common stock under employee stock purchase plan Stock Issued During Period, Shares, Employee Stock Purchase Plans Number of shares issued Issuance of common stock under employee stock purchase plan (in shares) Represents the aggregate change in value due to net settlement of taxes and/or exercise price of options exercised and/or RSUs vested during the period. Net settlement for taxes and/or exercise price related to equity awards Net settlement for taxes and/or exercise price related to equity awards Number of shares utilized in net settlement of taxes and/or exercise price of options exercised and/or RSUs vested during the period. Net settlement for taxes and/or exercise price related to equity awards (in shares) Net settlement for taxes and/or exercise price related to equity awards (in shares) Shares withheld in settlement of taxes and/or exercise price Stock Repurchased and Retired During Period, Value Repurchases of common shares Repurchases of common shares Stock Repurchased and Retired During Period, Shares Repurchases of common shares (in shares) Repurchases of common shares (in shares) Consolidated Statements of Cash Flows Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities: Net income Net income Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Share-based Compensation Stock-based compensation expense Depreciation, Depletion and Amortization Depreciation and amortization expense Deferred Income Tax Expense (Benefit) Deferred income tax benefit Provision for Doubtful Accounts Provision for doubtful accounts Charged to expense Accretion (Amortization) of Discounts and Premiums, Investments Net accretion of discounts and amortization of premiums on available-for-sale securities Amortization of Debt Issuance Costs Amortization of debt issuance costs Gain (Loss) on Disposition of Property Plant Equipment Loss on disposal of equipment Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable The increase (decrease) in the amount of capitalized contract costs due to netting additions and amortization during the reporting period. Increase Decrease In Capitalized Contract Cost Deferred contract costs Increase (Decrease) in Prepaid Expense Prepaid expenses and other Increase (Decrease) in Accounts Payable, Trade Accounts payable The increase (decrease) during the reporting period in the aggregate amount of expenses incurred but not yet paid and in liabilities classified as other. Increase Decrease In Accrued Liabilities And Other Liabilities Accrued expenses and other The increase (decrease) during the reporting period in the amount of lease allowances receivable from landlords for tenant improvements. Increase Decrease In Lease Allowance For Tenant Improvements Tenant improvement allowance Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities: Payments to Acquire Debt Securities, Available-for-sale Purchases of available-for-sale securities and other Proceeds from Sale and Maturity of Available-for-sale Securities Proceeds from sales and maturities of available-for-sale securities Payments to Develop Software Capitalized internal-use software costs Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Cash outflow used to perform tenant improvements to leased property. Payments For Improvements To Leased Property Lease allowances used for tenant improvements Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities: Represents the amount of net increase (decrease) in client funds obligation during the period. Increase (Decrease) in Client Funds Obligation Net change in client fund obligations Payments for Repurchase of Common Stock Repurchases of common shares Proceeds from Stock Options Exercised Proceeds from exercise of stock options Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Excluding Stock Options Proceeds from employee stock purchase plan Taxes paid related to net share settlement of equity awards Taxes paid related to net share settlement of equity awards Payments of Debt Issuance Costs Payment of debt issuance costs Net Cash Provided by (Used in) Financing Activities Net cash provided by (used in) financing activities Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Net change in cash, cash equivalents and funds held for clients' cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents and funds held for clients' cash and cash equivalents-end of period Cash, cash equivalents and funds held for clients' cash and cash equivalents-beginning of period Noncash Investing and Financing Items [Abstract] Supplemental Disclosure of Non-Cash Investing and Financing Activities Capital Expenditures Incurred but Not yet Paid Purchases of property and equipment, accrued but not paid Supplemental Cash Flow Information [Abstract] Supplemental Disclosure of Cash Flow Information Interest Paid, Excluding Capitalized Interest, Operating Activities Cash paid for interest Income Taxes Paid, Net Cash paid for income taxes, net of refunds No definition available Reconciliation of cash, cash equivalents and funds held for clients' cash and cash equivalents to the Consolidated Balance Sheets The amount of funds held for clients that are cash and cash equivalents. Funds held for clients' cash and cash equivalents Funds held for clients' cash and cash equivalents Fair value of funds held for clients' cash and cash equivalents Amount of cash and cash equivalents and funds held for clients cash and cash equivalents. Cash, cash equivalents and funds held for clients' cash and cash equivalent Total cash, cash equivalents and funds held for clients' cash and cash equivalents Organization and Description of Business Nature of Operations [Text Block] Organization and Description of Business Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Summary of Significant Accounting Policies Revenue Revenue from Contract with Customer [Text Block] Revenue Balance Sheet Information Supplemental Balance Sheet Disclosures [Text Block] Balance Sheet Information n/a Corporate Investments and Funds Held for Clients Schedule of funds held for clients and corporate investments, including client cash and cash equivalents and available-for-sale securities. Schedule Of Funds Held For Clients And Corporate Investments [Table] Schedule of Corporate Investments and Funds Held for Clients Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Funds Held For Clients And Corporate Investments [Line Items] Corporate Investments and Funds Held for Clients The entire disclosure for funds held for clients and corporate investments. Funds Held For Clients And Corporate Investments [Text Block] Corporate Investments and Funds Held for Clients Fair Value Measurement Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair value measurement Fair Value Disclosures [Text Block] Fair Value Measurement Debt Debt Disclosure [Text Block] Debt Leases Lessee, Operating Leases [Text Block] Leases Benefit Plans Defined Contribution Plan [Table] Defined Contribution Plan Disclosure [Line Items] Defined Contribution Plan Disclosure