Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Cash equivalents Money Market Funds [Member] Corporate debt securities Corporate Debt Securities [Member] U.S. Treasury, government and agency debt securities US Treasury and Government [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Available-for-sale Securities Available-for-sale Securities Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation, Stock Options, Activity Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Nonvested Restricted Stock Shares Activity Nonvested Restricted Stock Shares Activity [Table Text Block] Schedule of Nonvested Restricted Stock Units Activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs for all Plans Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Number of Shares Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Beginning balance Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Granted (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Canceled Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Ending balance Weighted-Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Beginning balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Canceled (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Ending balance (in dollars per share) Goodwill and Intangible Assets Disclosure [Abstract] Amortization expense of intangible assets Amortization of Intangible Assets Earnings Per Share [Abstract] Basic EPS: Earnings Per Share, Basic [Abstract] Net loss Net Income (Loss) Attributable to Parent Weighted-average common shares outstanding (in shares) Weighted Average Number of Shares Issued, Basic Weighted-average unvested restricted shares (in shares) Weighted Average Number of Shares, Restricted Stock Weighted-average shares used to compute net income (loss) per share (in shares) Weighted Average Number of Shares Outstanding, Basic Basic net income (loss) per share (usd per share) Earnings Per Share, Basic Diluted EPS: Earnings Per Share, Diluted [Abstract] Net loss Weighted-average shares used to compute diluted net income (loss) per share (in shares) Weighted Average Number of Shares Outstanding, Diluted Diluted net income (loss) per share (usd per share) Earnings Per Share, Diluted Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Cost of revenue Cost of Sales [Member] Sales and marketing Selling and Marketing Expense [Member] Technology and development Research and Development Expense [Member] General and administrative General and Administrative Expense [Member] Restructuring and other exit costs Restructuring Charges [Member] Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Stock-based compensation expense Allocated Share-based Compensation Expense Income Tax Disclosure [Abstract] Provision for income taxes Income Tax Expense (Benefit) Provisional Transition Tax recorded due to Tax Act Tax Cuts And Jobs Act Of 2017 Incomplete Accounting Provisional Income Tax Expense Benefit Amount of reasonable estimate for income tax expense (benefit) from effect of Tax Cuts and Jobs Act for which accounting for tax effect is incomplete. Provisional GILTI inclusion for ASC Topic 740 Global Intangible Low-Taxed Income (GILTI) Provisional Inclusion Global Intangible Low-Taxed Income (GILTI) Provisional Inclusion Balance Sheet Related Disclosures [Abstract] Weighted remaining contractual maturity Available-for-sale Securities, Weighted-average Remaining Contractual Maturity Available-for-sale Securities, Weighted-average Remaining Contractual Maturity Realized gains (losses) on available-for-sale securities Available-for-sale Securities, Gross Realized Gain (Loss) Unrealized holding gains (losses) reclassified out of AOCI into the statements of operations for the sale of AFS investments Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax Intangible Assets Intangible Assets Disclosure [Text Block] Unvested restricted stock awards Restricted Stock [Member] Unrecognized employee stock-based compensation Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Unrecognized employee stock-based compensation, period for recognition Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Fair value of restricted stock unit Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Expected term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Intent Marketing Solution Intent Marketing Solution [Member] Intent Marketing Solution [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenue Revenues Income Statement [Abstract] Expenses: Costs and Expenses [Abstract] Cost of revenue Cost of Revenue Sales and marketing Selling and Marketing Expense Technology and development Research and Development Expense General and administrative General and Administrative Expense Restructuring and other exit costs Restructuring Charges Total expenses Costs and Expenses Loss from operations Operating Income (Loss) Other (income) expense: Nonoperating Income (Expense) [Abstract] Interest income, net Interest Income (Expense), Net Other income Other Operating Income Foreign exchange loss, net Foreign Currency Transaction Gain (Loss), before Tax Total other (income) expense, net Nonoperating Income (Expense) Loss before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Net loss Net loss per share: Basic (usd per share) Diluted (usd per share) Weighted-average shares used to compute net loss per share: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Stock Option Employee Stock Option [Member] Employee Stock Employee Stock [Member] Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Revenues Revenue from Contract with Customer [Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Marketable securities Marketable Securities Accounts receivable, net Accounts Receivable, Net, Current Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current TOTAL CURRENT ASSETS Assets, Current Property and equipment, net Property, Plant and Equipment, Net Internal use software development costs, net Internal Use Software Development Costs, Net The carrying amount of internal use software development costs net of accumulated amortization as of the balance sheet date. Other assets, non-current Other Assets, Noncurrent Intangible assets, net Intangible Assets, Net (Excluding Goodwill) TOTAL ASSETS Assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] LIABILITIES Liabilities [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities, Current Other current liabilities Other Liabilities, Current TOTAL CURRENT LIABILITIES Liabilities, Current Other liabilities, non-current Other Liabilities, Noncurrent TOTAL LIABILITIES Liabilities Commitments and contingencies (Note 10) Commitments and Contingencies STOCKHOLDERS' EQUITY Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.00001 par value, 10,000 shares authorized at March 31, 2018 and December 31, 2017; 0 shares issued and outstanding at March 31, 2018 and December 31, 2017 Preferred Stock, Value, Issued Common stock, $0.00001 par value; 500,000 shares authorized at March 31, 2018 and December 31, 2017; 50,280 and 50,239 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated deficit Retained Earnings (Accumulated Deficit) TOTAL STOCKHOLDERS' EQUITY Stockholders' Equity Attributable to Parent TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity Income Taxes Income Tax Disclosure [Text Block] Risk-free interest rate (in percentage) Expected volatility (in percentage) Dividend yield (in percentage) Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Number of shares available for grant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Number of shares reserved Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Restricted awards Restricted awards [Member] Restricted awards including RSAs and RSUs Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Two Year RSUs Two Year RSUs [Member] Two Year RSUs [Member] Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Award vesting rights, percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Number of awards granted Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted Restructuring and Related Activities [Abstract] Schedule of Restructuring and Related Costs [Table] Schedule of Restructuring and Related Costs [Table] Restructuring Type [Axis] Restructuring Type [Axis] Type of Restructuring [Domain] Type of Restructuring [Domain] Non-cash stock-based compensation Noncash Stock Based Compensation [Member] Noncash Stock Based Compensation [Member] Restructuring Plan [Axis] Restructuring Plan [Axis] Restructuring Plan [Domain] Restructuring Plan [Domain] The 2017 Restructuring Events The 2017 Restructuring Events [Member] The 2017 Restructuring Events [Member] The 2018 Restructuring Events The 2018 Restructuring Events [Member] The 2018 Restructuring Events [Member] Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Restructuring and other exit costs Accrued restructuring costs Restructuring Reserve Restructuring Reserve [Roll Forward] Restructuring Reserve [Roll Forward] Accrued restructuring and other exit costs at December 31, 2017 Cash paid for restructuring and other exit costs Payments for Restructuring Non-cash stock-based compensation for restructuring and other exit costs Restructuring Reserve, Settled without Cash Accrued restructuring and other exit costs at March 31, 2018 Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Options to purchase common stock Equity Option [Member] Unvested restricted stock units ESPP Employee Stock Purchase Plan [Member] Employee Stock Purchase Plan [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Total shares excluded from net income (loss) per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2014 Employee Stock Purchase Plan 2014 Employee Stock Purchase Plan [Member] 2014 Employee Stock Purchase Plan [Member] Maximum employee subscription rate Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate Purchase price of common stock, percent Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Grant date fair value Intrinsic value of nonvested unit Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested Employee Service Share-Based Compensation, Non-Vested Restricted Stock Units, Compensation Cost Not Yet Recognized, Period for Recognition Employee Service Share-Based Compensation, Non-Vested Restricted Stock Units, Compensation Cost Not Yet Recognized, Period for Recognition Employee Service Share-Based Compensation, Non-Vested Restricted Stock Units, Compensation Cost Not Yet Recognized, Period for Recognition Fair Value, Assets Measured on Recurring Basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Available-for-sale—short-term Short-term Investments [Member] Available-for-sale — long-term Other Long-term Investments [Member] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] U.S. Treasury, government and agency debt securities Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Amortized Cost Available-for-sale Debt Securities, Amortized Cost Basis Gross Unrealized Gains Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Losses Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax Fair Value Available-for-sale Securities, Debt Securities Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Accumulated Deficit Retained Earnings [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance (in shares) Common Stock, Shares, Outstanding Beginning Balance Exercise of common stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of common stock options Stock Issued During Period, Value, Stock Options Exercised Issuance of common stock related to RSU vesting (in shares) Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Shares withheld related to net share settlement (in shares) Shares Paid for Tax Withholding for Share Based Compensation Shares withheld related to net share settlement Adjustments Related to Tax Withholding for Share-based Compensation Stock-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Ending Balance (in shares) Ending Balance Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States UNITED STATES United Kingdom UNITED KINGDOM Other international Other International [Member] Other International [Member] Accounts payable—seller Accounts Payable, Seller, Current Description of balance sheet netting of assets and liabilities per ASC 210-20. Accounts payable—trade Accounts Payable, Trade, Current Accrued employee-related payables Employee-related Liabilities, Current Accounts payable and accrued expenses Restricted cash Restricted Cash Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Stock-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Other Commitments [Table] Other Commitments [Table] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] Data Centers For Cloud-Based Services Data Centers For Cloud-Based Services [Member] Data Centers For Cloud-Based Services [Member] Office Lease Office Lease [Member] Office Lease [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Financial Standby Letter of Credit Financial Standby Letter of Credit [Member] Other Commitments [Line Items] Other Commitments [Line Items] Rental expense Operating Leases, Rent Expense Letters of credit outstanding, amount Letters of Credit Outstanding, Amount Net Income (Loss) Per Share Earnings Per Share [Text Block] Accounting Policies [Abstract] Basis of Presentation and Summary of Significant Accounting Policies Basis of Accounting, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Restricted Stock Awards Organization and Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Restructuring and Other Exit Costs Restructuring and Related Activities Disclosure [Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Developed technology Developed Technology Rights [Member] Non-compete agreements Noncompete Agreements [Member] Trademarks Trademarks [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Amortizable intangible assets, gross Finite-Lived Intangible Assets, Gross Total accumulated amortization—intangible assets Finite-Lived Intangible Assets, Accumulated Amortization Total Finite-Lived Intangible Assets, Net Investments in Marketable Securities Marketable Securities [Table Text Block] Schedule of Accounts Payable and Accrued Liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Statement of Comprehensive Income [Abstract] Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Unrealized loss on investments Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule of Restructuring and Other Exit Costs Restructuring and Related Costs [Table Text Block] Preferred stock, shares authorized Preferred Stock, Shares Authorized Preferred stock, par or stated value per share (usd per share) Preferred Stock, Par or Stated Value Per Share 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 or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares, issued Common Stock, Shares, Issued Common stock, shares, outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Gross Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Gross Expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Ending balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Beginning balance (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Exercised (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Expired (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Forfeited (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value Ending balance (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Outstanding, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Exercisable (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Exercisable (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Exercisable, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Schedule of Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Schedule of Finite-Lived Intangible Assets, Future Amortization Expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Other Balance Sheet Amounts Supplemental Balance Sheet Disclosures [Text Block] Statement of Cash Flows [Abstract] OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Stock-based compensation Share-based Compensation Loss on disposal of property and equipment Gain (Loss) on Disposition of Property Plant Equipment Provision for doubtful accounts Provision for Doubtful Accounts Accretion of available for sale securities Accretion Of Available-For-Sale Securities Accretion Of Available-For-Sale Securities Unrealized foreign currency gains, net Foreign Currency Transaction Gain (Loss), Unrealized Deferred income taxes Deferred Income Taxes and Tax Credits Changes in operating assets and liabilities, net of effect of business acquisitions: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Operating Activities INVESTING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Capitalized internal use software development costs Payments to Develop Software Investments in available-for-sale securities Payments to Acquire Available-for-sale Securities Maturities of available-for-sale securities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Proceeds from exercise of stock options Proceeds from Stock Options Exercised Taxes paid related to net share settlement Payments Related to Tax Withholding for Share-based Compensation Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities EFFECT OF EXCHANGE RATE CHANGES ON CASH, CASH EQUIVALENTS AND RESTRICTED CASH Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of period SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION: Supplemental Cash Flow Information [Abstract] Capitalized assets financed by accounts payable and accrued expenses Capital Expenditures Incurred but Not yet Paid Capitalized stock-based compensation Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Remaining 2018 Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Intrinsic values of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Unrecognized employee stock-based compensation Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Weighted average grant date fair value Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Options outstanding (in shares) Fair value of options vested in period Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value