Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Schedule of Other Assets Schedule of Other Assets [Table Text Block] Lease deposits Security Deposit Derivative instruments Derivative Asset Deposits with statutory authorities Deposit Assets Term deposits Time Deposits, at Carrying Value Contract assets Contract with Customer, Asset, Gross, Noncurrent Deferred contract fulfillment costs Deferred Contract Acquisition Costs NonCurrent Deferred Contract Acquisition Costs NonCurrent Others Other Assets, Miscellaneous Other assets Other Assets Leases [Abstract] Operating Leases Operating Lease Liabilities, Payments Due [Abstract] 2019 (April 1 - December 31) Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two 2021 Lessee, Operating Lease, Liability, Payments, Due Year Three 2022 Lessee, Operating Lease, Liability, Payments, Due Year Four 2023 Lessee, Operating Lease, Liability, Payments, Due Year Five 2024 Lessee, Operating Lease, Liability, Payments, Due Year Six Lessee, Operating Lease, Liability, Payments, Due Year Six 2025 and thereafter Lessee, Operating Lease, Liability, Payments, Due after Year Six Lessee, Operating Lease, Liability, Payments, Due after Year Six Total lease payments Lessee, Operating Lease, Liability, Payments, Due Less: Imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Lease liabilities Operating Lease, Liability Finance Leases Finance Lease Liabilities, Payments, Due [Abstract] 2019 (April 1 - December 31) Finance Lease, Liability, Payments, Remainder of Fiscal Year 2020 Finance Lease, Liability, Payments, Due Year Two 2021 Finance Lease, Liability, Payments, Due Year Three 2022 Finance Lease, Liability, Payments, Due Year Four 2023 Finance Lease, Liability, Payments, Due Year Five 2024 Finance Lease, Liability, Payments, Due Year Six Finance Lease, Liability, Payments, Due Year Six 2025 and thereafter Finance Lease, Liability, Payments, Due after Year Six Finance Lease, Liability, Payments, Due after Year Six Total lease payments Finance Lease, Liability, Payments, Due Less: Imputed interest Finance Lease, Liability, Undiscounted Excess Amount Lease liabilities Finance Lease, Liability Payables and Accruals [Abstract] Accrued expenses Accrued Expenses Current Accrued expenses. Derivative instruments Derivative Instruments and Hedges, Liabilities Client liabilities Payables to Customers Other current liabilities Other Liabilities, Current Accrued expenses and other current liabilities Accrued Liabilities, Current Equity [Abstract] Class of Treasury Stock [Table] Class of Treasury Stock [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] 2014 Repurchase Program Two Thousand Fourteen Repurchase Program [Member] Two thousand fourteen repurchase program. 2017 Repurchase Program Two Thousand Seventeen Repurchase Program [Member] Two Thousand Seventeen Repurchase Program [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Number of classes of common stock outstanding Number Of Classes Of Common Stock Outstanding Number Of Classes Of Common Stock Outstanding Acquisition of restricted stock from employees in connection with withholding tax payments (in shares) Shares Paid for Tax Withholding for Share Based Compensation Withholding tax payments related to the vesting of restricted stock for total consideration Payments Related to Tax Withholding for Share-based Compensation Weighted average purchase price prior to the vesting date (in dollars per share) Accelerated Share Repurchases, Final Price Paid Per Share Repurchase of common stock authorized, maximum Stock Repurchase Program, Authorized Amount Additional authorized amount Stock Repurchase Program, Additional Authorized Amount Stock Repurchase Program, Additional Authorized Amount Authorized increase in repurchase amount Stock Repurchase Program, Authorized Increase in Repurchase Amount Per Period Stock Repurchase Program, Authorized Increase in Repurchase Amount Per Period Authorized increase in repurchase amount, 2018 Stock Repurchase Program, Authorized Increase in Repurchase Amount Per Period, Year Two Stock Repurchase Program, Authorized Increase in Repurchase Amount Per Period, Year Two Common stock purchased under the repurchase program (in shares) Treasury Stock, Shares, Acquired Common stock aggregate purchase price including commissions Common Stock Aggregate Purchase Price Including Commission Common stock aggregate purchase price including commission. Common stock average purchase price per share (in dollars per share) Treasury Stock Acquired, Average Cost Per Share Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Corridor Corridor Platform Inc [Member] Corridor Platform Inc [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Aggregate cost Equity Method Investment, Aggregate Cost Loss from equity-method investment Income (Loss) from Equity Method Investments Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Derivatives in cash flow hedging relationships Cash Flow Hedging [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Derivatives in hedging relationships Designated as Hedging Instrument [Member] Derivatives not designated as hedging instruments Not Designated as Hedging Instrument [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Foreign currency exchange contracts Foreign Exchange Contract [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Derivatives in cash flow hedging relationships Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax Gain/(loss) recognized in unaudited consolidated statements of income Foreign Currency Transaction Gain (Loss), before Tax Cash paid for amounts included in the measurement of lease liabilities : Cash Flow, Operating Activities, Lessee [Abstract] Operating cash flows from operating leases Operating Lease, Payments Operating cash flows from finance leases Finance Lease, Interest Payment on Liability Financing cash flows from finance leases Finance Lease, Principal Payments Weighted-average remaining lease term Weighted-Average Remaining Lease Term [Abstract] Weighted-Average Remaining Lease Term [Abstract] Finance lease Finance Lease, Weighted Average Remaining Lease Term Operating lease Operating Lease, Weighted Average Remaining Lease Term Weighted-average discount rate Weighted-Average Discount Rate [Abstract] Weighted-Average Discount Rate [Abstract] Finance lease Finance Lease, Weighted Average Discount Rate, Percent Operating lease Operating Lease, Weighted Average Discount Rate, Percent Segment Reporting [Abstract] Revenues and Cost of Revenues for Company's Reportable Segments Schedule of Segment Reporting Information, by Segment [Table Text Block] Revenues Based on Geographical Information Revenue from External Customers by Geographic Areas [Table Text Block] Property, Plant and Equipment based on Geographical Information Long-lived Assets by Geographic Areas [Table Text Block] Debt Disclosure [Abstract] Borrowings Debt Disclosure [Text Block] Retirement Benefits [Abstract] Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Plan assets at January 1, 2019 Defined Benefit Plan, Plan Assets, Amount Actual return Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Employer contribution Defined Benefit Plan, Plan Assets, Contributions by Employer Benefits paid Defined Benefit Plan, Plan Assets, Benefits Paid Effect of exchange rate changes Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) Plan assets at March 31, 2019 Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2018 Omnibus Incentive Plan [Member] 2018 Omnibus Incentive Plan [Member] 2018 Omnibus Incentive Plan [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number available for grant (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Revenue from Contract with Customer [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Capitalized Contract Cost [Axis] Capitalized Contract Cost [Axis] Capitalized Contract Cost [Domain] Capitalized Contract Cost [Domain] Contract Acquisition Costs Contract Acquisition Costs [Member] Contract Acquisition Costs [Member] Contract Fulfillment Costs Contract Fulfillment Costs [Member] Contract Fulfillment Costs [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Accounts receivable not billed Unbilled Contracts Receivable Contract liability, revenue recognized Contract with Customer, Liability, Revenue Recognized Capitalized contract acquisition costs Capitalized Contract Cost, Gross Increase in capitalized contract costs Increase In Capitalized Contract Cost Gross Increase In Capitalized Contract Cost Gross Capitalized contract acquisition costs, amount amortized Capitalized Contract Cost, Amortization Impairment loss in relation to costs capitalized Capitalized Contract Cost, Impairment Loss Deferred costs, contract fulfillment Amount of Deferred Costs Related to Long-term Contracts Contracts with Customer, Receivables and Liabilities Contract with Customer, Asset and Liability [Table Text Block] Business Combination, Goodwill And Intangible Assets Disclosure [Abstract] Business Combination, Goodwill And Intangible Assets Disclosure [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Health Integrated, Inc. Health Integrated, Inc. [Member] Health Integrated, Inc. [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Insurance Insurance [Member] Insurance [Member] Healthcare Health Care [Member] TT&L Travel, Transportation and Logistics [Member] Travel, Transportation and Logistics [Member] F&A Finance and Accounting [Member] Finance and Accounting [Member] All Other Other Operations Management [Member] Other Operations Management [Member] Analytics Analytics [Member] Analytics [Member] Goodwill [Line Items] Goodwill [Line Items] Finite-Lived Intangible Assets, Accumulated Impairment Finite-Lived Intangible Assets, Accumulated Impairment Finite-Lived Intangible Assets, Accumulated Impairment Goodwill [Roll Forward] Goodwill [Roll Forward] Beginning Balance Goodwill Acquisitions Goodwill, Acquired During Period Measurement period adjustments Goodwill, Purchase Accounting Adjustments Currency translation adjustments Goodwill, Foreign Currency Translation Gain (Loss) Impairment charges Goodwill, Impairment Loss Ending Balance Statement of Financial Position [Abstract] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, issued (in shares) Preferred Stock, Shares Issued Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, authorized (in shares) Common Stock, Shares Authorized Common stock, issued (in shares) Common Stock, Shares, Issued Common stock, outstanding (in shares) Common Stock, Shares, Outstanding Treasury stock (in shares) Treasury Stock, Shares Derivatives Designated as Hedging Instruments Cost of revenues Cost of Goods and Services Sold General and administrative expenses General and Administrative Expense Selling & marketing expenses Selling and Marketing Expense Depreciation & amortization Depreciation, Depletion and Amortization, Nonproduction Reclassification from AOCI, before tax Reclassification from AOCI, Current Period, before Tax, Attributable to Parent Foreign exchange gain, net Accounting Policies [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash (current) Restricted Cash, Current Restricted cash (non-current) Restricted Cash, Noncurrent Cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Schedule of Other Current Assets Schedule of Other Current Assets [Table Text Block] Income Statement [Abstract] Revenues, net Revenue from Contract with Customer, Excluding Assessed Tax Cost of revenues Cost of Services, Excluding Depreciation, Depletion, and Amortization Gross profit Gross Profit Operating expenses: Operating Expenses [Abstract] General and administrative expenses Selling and marketing expenses Depreciation and amortization Impairment charges Capitalized Computer Software, Impairments Total operating expenses Operating Expenses Income from operations Operating Income (Loss) Interest expense Interest Expense Other income, net Other Nonoperating Income (Expense) Income before income tax expense/(benefit) and earnings from equity affiliates Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax expense/(benefit) Income Tax Expense (Benefit) Income before earnings from equity affiliates Income (Loss) From Continuing Operations Before Equity Method Investments, Total Income (Loss) From Continuing Operations Before Equity Method Investments, Total Loss from equity-method investment Net income attributable to ExlService Holdings, Inc. stockholders Net Income (Loss) Attributable to Parent Earnings per share attributable to ExlService Holdings, Inc. stockholders: Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Weighted-average number of shares used in computing earnings per share attributable to ExlService Holdings, Inc. stockholders: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Performance Based Stock Awards Performance Based Stock Awards [Member] Performance Based Stock Awards [Member] Unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Cost not yet recognized, period for recognition Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Stock Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Schedule of costs related to company's stock-based compensation plan Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Schedule of stock options activity Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of restricted stock and RSU activity Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Schedule of performance based stock awards activity Share-based Compensation, Performance Shares Award Outstanding Activity [Table Text Block] Earnings Per Share Earnings Per Share [Text Block] Assets Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Short-term investments Short-term Investments Restricted cash Accounts receivable, net Accounts Receivable, Net, Current Prepaid expenses Prepaid Expense, Current Advance income tax, net Prepaid Taxes Other current assets Other Assets, Current Total current assets Assets, Current Property and equipment, net Property, Plant and Equipment, Net Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Restricted cash Deferred tax assets, net Deferred Income Tax Assets, Net Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Goodwill Other assets Other Assets, Noncurrent Investment in equity affiliate Equity Method Investments Total assets Assets Liabilities and equity Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Current portion of long-term borrowings Long-term Debt, Current Maturities Deferred revenue Contract with Customer, Liability, Current Accrued employee costs Employee-related Liabilities, Current Accrued expenses and other current liabilities Current portion of operating lease liabilities Operating Lease, Liability, Current Income taxes payable Accrued Income Taxes, Current Current portion of finance lease obligations Finance Lease, Liability, Current Total current liabilities Liabilities, Current Long term borrowings Long-term Debt, Excluding Current Maturities Finance lease obligations, less current portion Finance Lease, Liability, Noncurrent Deferred tax liabilities, net Deferred Income Tax Liabilities, Net Operating lease liabilities, less current portion Operating Lease, Liability, Noncurrent Other non-current liabilities Liabilities, Other than Long-term Debt, Noncurrent Total liabilities Liabilities Commitments and contingencies (Refer Note 26) Commitments and Contingencies Preferred stock, $0.001 par value; 15,000,000 shares authorized, none issued Preferred Stock, Value, Issued ExlService Holdings, Inc. Stockholders’ equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Common stock, $0.001 par value; 100,000,000 shares authorized, 38,256,036 shares issued and 34,365,437 shares outstanding as of March 31, 2019 and 37,850,544 shares issued and 34,222,476 shares outstanding as of December 31, 2018 Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total including shares held in treasury Stockholders Equity Including Shares Held In Treasury Total stockholders' equity including shares held in treasury. Less: 3,890,599 shares as of March 31, 2019 and 3,628,068 shares as of December 31, 2018, held in treasury, at cost Treasury Stock, Value Stockholders’ equity Stockholders' Equity Attributable to Parent Non-controlling interest Stockholders' Equity Attributable to Noncontrolling Interest Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total liabilities and equity Liabilities and Equity Segment and Geographical Information Segment Reporting Disclosure [Text Block] Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Schedule of Accumulated Other Comprehensive Loss Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Property, Plant and Equipment [Abstract] Property and Equipment, net Property, Plant and Equipment Disclosure [Text Block] Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net income Adjustments to reconcile net income to net cash provided/(used for) by 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 expense Share-based Compensation Unrealized gain on short term investments Unrealized Gain (Loss) on Investments Unrealized foreign exchange loss/(gain), net Foreign Currency Transaction Gain (Loss), Unrealized Deferred income tax expense Deferred Income Tax Expense (Benefit) Allowance for doubtful accounts receivable Provision for Doubtful Accounts Amortization of non-cash interest expense related to convertible senior notes Amortization of Debt Discount (Premium) Others, net Other Noncash Income (Expense) Change in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Advance income tax, net Increase (Decrease) in Income Taxes Payable Other assets Increase (Decrease) in Other Operating Assets Accounts payable Increase (Decrease) in Accounts Payable Deferred revenue Increase (Decrease) in Contract with Customer, Liability Accrued employee costs Increase (Decrease) in Other Employee-Related Liabilities Accrued expenses and other liabilities Increase (Decrease) in Other Accounts Payable and Accrued Liabilities Net cash provided by/(used for) operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Purchase of property and equipment Payments to Acquire Property, Plant, and Equipment Business acquisition (net of cash acquired) Payments to Acquire Businesses, Net of Cash Acquired Purchase of investments Payments to Acquire Investments Proceeds from redemption of investments Proceeds from Sale, Maturity and Collection of Investments Net cash used for investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Principal payments on finance lease obligations Repayments of Long-term Capital Lease Obligations Proceeds from borrowings Proceeds from Issuance of Long-term Debt Repayments of borrowings Repayments of Debt Payment of debt issuance costs Payments of Debt Issuance Costs Acquisition of treasury stock Payments for Repurchase of Common Stock Proceeds from exercise of stock options Proceeds from Stock Options Exercised Net cash provided by/(used for) 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 Net decrease 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 at beginning of period Cash, cash equivalents and restricted cash at end of period Other Income and Expenses [Abstract] Other Income, net Interest and Other Income [Text Block] Business Combinations, Goodwill and Intangible Assets Business Combination, Goodwill And Intangible Assets Disclosure [Text Block] Business Combination, Goodwill And Intangible Assets Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] 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 and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] 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] Assets Assets, Fair Value Disclosure [Abstract] Mutual funds Money Market And Mutual Fund Fair Value Disclosure Money market and mutual fund fair value disclosure. Derivative financial instruments Foreign Currency Contract, Asset, Fair Value Disclosure Total Assets, Fair Value Disclosure Liabilities Liabilities, Fair Value Disclosure [Abstract] Derivative financial instruments Foreign Currency Contracts, Liability, Fair Value Disclosure Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Line of Credit Facility [Table] Line of Credit Facility [Table] SCIO SCIO [Member] SCIO [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] New Credit Agreement New Credit Agreement [Member] New Credit Agreement [Member] 3.50% Convertible Senior Notes due October 1, 2024 3.50% Convertible Senior Notes due October 1, 2024 [Member] 3.50% Convertible Senior Notes due October 1, 2024 [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Prime Rate Prime Rate [Member] London Interbank Offered Rate (LIBOR) London Interbank Offered Rate (LIBOR) [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Convertible Notes Payable Convertible Notes Payable [Member] Notes Payable, Other Payables Notes Payable, Other Payables [Member] Credit Facilities [Line Items] Line of Credit Facility [Line Items] Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Option to increase additional credit facility Line Of Credit Facility Option For Additional Borrowing Capacity Line of credit facility option for additional borrowing capacity. Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Commitment fee percentage range on unused credit facility Line of Credit Facility, Commitment Fee Percentage Line of credit interest rate during period Line of Credit Facility, Interest Rate During Period Unrestricted domestic cash and cash equivalents threshold Debt Instrument, Covenant, Domestic Cash and Cash Equivalents Threshold Debt Instrument, Covenant, Domestic Cash and Cash Equivalents Threshold Interest coverage ratio, minimum Debt Instrument, Covenant, Interest Coverage Ratio, Minimum Debt Instrument, Covenant, Interest Coverage Ratio, Minimum Leverage ratio, maximum Debt Instrument, Covenant, Leverage Ratio, Maximum Debt Instrument, Covenant, Leverage Ratio, Maximum Outstanding debt Long-term Line of Credit Long-term debt, maturities, repayments of principal in next twelve months Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months Outstanding debt, noncurrent Long-term Line of Credit, Noncurrent Outstanding debt, current Line of Credit, Current Unamortized debt issuance costs Debt Issuance Costs, Net Debt instrument face amount Debt Instrument, Face Amount Interest rate Debt Instrument, Interest Rate, Stated Percentage Interest expense Interest Expense, Debt Conversion rate Debt Instrument, Convertible, Conversion Ratio Debt instrument, conversion price (in dollars per share) Debt Instrument, Convertible, Conversion Price Threshold percentage of stock price trigger Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger Repayments of outstanding borrowings Repayments of Lines of Credit Net proceeds from convertible notes Proceeds from Debt, Net of Issuance Costs Debt issuance costs Debt Issuance Costs, Gross Payment of debt issuance costs Liability component of debt issuance costs Debt Issuance Costs, Net, Liability Component Debt Issuance Costs, Net, Liability Component Equity component of debt issuance costs Debt Issuance Costs, Net, Equity Component Debt Issuance Costs, Net, Equity Component Unamortized debt issuance costs Unamortized Debt Issuance Expense Convertible notes, liability component Convertible Debt, Fair Value Disclosures Convertible senior notes, interest rate Debt Instrument, Interest Rate, Effective Percentage Allocation of equity component related to issuance costs on convertible senior notes Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt Remaining discount amortization period Debt Instrument, Convertible, Remaining Discount Amortization Period Debt discount amortization Structured payable Long-term Debt Number of operating segments Number of Operating Segments Number of operating segments, operations management Number of Operating Segments, Operations Management Services Number of Operating Segments, Operations Management Services Number of operating segments, industry focused Number of Operating Segments, Industry Focused Number of Operating Segments, Industry Focused Number of operating segments, finance and accounting Number of Operating Segments, Finance and Accounting Services Number of Operating Segments, Finance and Accounting Services Number of operating segments, company provides operations management services Number of Operating Segments, Company Provides Operations Management Services Number of Operating Segments, Company Provides Operations Management Services Number of non-operations management services Number of Operating Segments, Non-Operations Management Services Number of Operating Segments, Non-Operations Management Services Income Tax Disclosure [Abstract] Effective tax rate, current income tax expense (benefit) Effective Income Tax Rate Reconciliation, Percent Excess tax benefits, stock awards Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Measurement period adjustment, transition tax increase (decrease) Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit) Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit) Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Revolver Credit Notes Structured Payables Debt Instrument [Line Items] Debt Instrument [Line Items] 2019 (April - December) Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year 2020 Long-term Debt, Maturities, Repayments of Principal in Year Two 2021 Long-term Debt, Maturities, Repayments of Principal in Year Three 2022 Long-term Debt, Maturities, Repayments of Principal in Year Four 2023 Long-term Debt, Maturities, Repayments of Principal in Year Five Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Total Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Depreciation and Amortization Depreciation And Amortization [Member] Depreciation And Amortization [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Depreciation and amortization expense Depreciation Effect of the foreign exchange gains upon settlement of cash flow hedges Gain (Loss) on Hedging Activity Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Operating Lease Operating Leases [Abstract] Operating Leases [Abstract] Operating lease liabilities - Current Operating lease liabilities - Non-current Total operating lease liabilities Finance Lease Finance Leases [Abstract] Finance Leases [Abstract] Property and equipment, gross Finance Lease, Right-of-Use Asset, Gross Finance Lease, Right-of-Use Asset, Gross Accumulated depreciation Finance Lease, Right-of-Use, Accumulated Amortization Finance Lease, Right-of-Use, Accumulated Depreciation Property and equipment, net Finance Lease, Right-of-Use Asset Finance lease liabilities - Current Finance lease liabilities - Non-current Total finance lease liabilities Operating Leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2019 Operating Leases, Future Minimum Payments, Next Rolling Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Rolling Year Two 2021 Operating Leases, Future Minimum Payments, Due in Rolling Year Three 2022 Operating Leases, Future Minimum Payments, Due in Rolling Year Four 2023 Operating Leases, Future Minimum Payments, Due in Rolling Year Five 2024 Operating Leases, Future Minimum Payments, Due in Rolling Year Six Operating Leases, Future Minimum Payments, Due in Rolling Year Six 2025 and thereafter Operating Leases, Future Minimum Payments, Due After Year Six Operating Leases, Future Minimum Payments, Due After Year Six Total minimum lease payment Operating Leases, Future Minimum Payments Due Capital Leases Capital Leases, Future Minimum Payments, Net Present Value [Abstract] 2019 Capital Leases, Future Minimum Payments, Next Rolling Twelve Months 2020 Capital Leases, Future Minimum Payments, Due in Rolling Year Two 2021 Capital Leases, Future Minimum Payments, Due in Rolling Year Three 2022 Capital Leases, Future Minimum Payments, Due in Rolling Year Four 2023 Capital Leases, Future Minimum Payments, Due in Rolling after Year Five 2024 Capital Leases, Future Minimum Payments, Due in Rolling Year Six Capital Leases, Future Minimum Payments, Due in Rolling Year Six 2025 and thereafter Capital Leases, Future Minimum Payments, Due in Rolling after Year Six Capital Leases, Future Minimum Payments, Due in Rolling after Year Six Total minimum lease payment Capital Leases, Future Minimum Payments Due Less: Imputed interest Capital Leases, Future Minimum Payments, Interest Included in Payments Present value of minimum lease payments Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments Less: Current portion Capital Lease Obligations, Current Long term capital lease obligation Capital Lease Obligations, Noncurrent Expected return on plan assets, percentage Defined Benefit Plan Expected Return On Plan Assets Percentage Defined Benefit Plan Expected Return On Plan Assets Percentage Discretionary contributions towards 401(k) plan, maximum percentage Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Discretionary contributions to 401(k) plans Defined Contribution Plan, Employer Discretionary Contribution Amount Defined contribution plan, cost Defined Contribution Plan, Cost Accounts receivable, net Contract assets Contract with Customer, Asset, Gross Contract liabilities: Contract with Customer, Liability [Abstract] Deferred revenue (advance payments portion) Contract with Customer, Liability Consideration received from customer for transitions activities Contract From Customer Liability,, Consideration Received From Transitions Activities Contract From Customer Liability, Consideration Received From Transitions Activities Amortization expense Amortization of Intangible Assets Revenue from External Customers by Products and Services [Table] Revenue from External Customers by Products and Services [Table] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] BPM and related services BPM and Related Services [Member] BPM and Related Services [Member] Analytics services Analytics Services [Member] Analytics Services [Member] Revenues and cost of revenues for Company's reportable segments [Line Items] Revenue from External Customer [Line Items] Operating expenses Foreign exchange gain, interest expense and other income, net Nonoperating Income (Expense) Number of capability operating segments Basis of Preparation Basis of Accounting, Policy [Policy Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Employee Benefits Pension and Other Postretirement Plans, Nonpension Benefits, Policy [Policy Text Block] Cash and Cash Equivalents and Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Accounts Receivable Receivables, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Recent Accounting Pronouncements and Recently Adopted Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Statement of Comprehensive Income [Abstract] Other comprehensive income/(loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Unrealized gain/(loss) on effective cash flow hedges, net of taxes $1,189 and ($800), respectively Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Foreign currency translation gain/(loss) Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Reclassification adjustments Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] Gain on cash flow hedges, net of taxes $354 and ($776), respectively Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Retirement benefits, net of taxes $109 and $1, respectively Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Total other comprehensive income/(loss) Other Comprehensive Income (Loss), Net of Tax Total comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] India INDIA United States UNITED STATES Philippines PHILIPPINES Rest of World Rest Of World [Member] Rest of World. Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Income Taxes Income Tax Disclosure [Text Block] Schedule of Accrued Expenses and Other Current Liabilities Schedule of Accrued Liabilities [Table Text Block] Derivatives and Hedge Accounting Derivative Instruments and Hedging Activities Disclosure [Text Block] Liabilities, Noncurrent [Abstract] Derivative instruments Derivative Instruments and Hedges, Liabilities, Noncurrent Unrecognized tax benefits Liability for Uncertainty in Income Taxes, Noncurrent Deferred rent Deferred Rent Credit, Noncurrent Retirement benefits Liability, Defined Benefit Plan, Noncurrent Deferred transition revenue Contract with Customer, Liability, Noncurrent Others Other Liabilities, Noncurrent Other non-current liabilities Restructuring and Related Activities [Abstract] Exit Cost Restructuring and Related Activities Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Summary of Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Other Non-Current Liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Noncurrent [Text Block] 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] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive (Loss)/Income AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock [Member] Non - Controlling Interest Noncontrolling Interest [Member] Statement [Line Items] Statement [Line Items] Beginning balance (in shares) Beginning balance Impact of adoption of ASU 2016-09 Cumulative Effect of New Accounting Principle in Period of Adoption Adjusted equity balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance Stock issued against stock-based compensation plans (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Stock issued against stock-based compensation plans Stock Issued During Period, Value, Stock Options Exercised Stock-based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Acquisition of treasury stock (in shares) Acquisition of treasury stock Acquisition Of Treasury Stock Value Equity impact of the value of stock that has been repurchased during the period and has not been retired and is held in treasury. Non-controlling interest Noncontrolling Interest, Period Increase (Decrease) Other comprehensive income Ending balance (in shares) Ending balance Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other current assets Other Current Assets [Member] Other assets Other Assets [Member] Accrued expenses and other current liabilities Accrued Expenses And Other Current Liabilities [Member] Accrued expenses and other current liabilities. Other non-current liabilities Other Noncurrent Liabilities [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Foreign currency exchange contracts, asset Derivative Asset, Fair Value, Gross Asset Foreign currency exchange contracts, liability Derivative Liability, Fair Value, Gross Liability Finance lease: Finance Lease, Cost [Abstract] Amortization of right-of-use assets Finance Lease, Right-of-Use Asset, Amortization Interest on lease liabilities Finance Lease, Interest Expense Operating lease Operating Lease, Cost Total lease cost Lease, Cost Operating lease costs for leases classified as such under Topic 840 Operating Leases, Rent Expense Document And Entity Information [Abstract] Document and entity information. Document Type Document Type Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Trading Symbol Trading Symbol Document Fiscal Period Focus Document Fiscal Period Focus Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Derivative instruments Derivative Asset, Current Advances to suppliers Prepaid Supplies Receivables from statutory authorities Service Taxes Receivable, Current Service Taxes Receivable, Current Contract assets Contract with Customer, Asset, Gross, Current Deferred contract fulfillment costs Deferred Contract Acquisition Costs Current Deferred Contract Acquisition Costs Current Others Other Assets, Miscellaneous, Current Other current assets Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Network equipment and computers Technology Equipment [Member] Software Software and Software Development Costs [Member] Leasehold improvements Leasehold Improvements [Member] Office furniture and equipment Furniture and Fixtures [Member] Motor vehicles Vehicles [Member] Buildings Building [Member] Land Land [Member] Capital work in progress Construction in Progress [Member] Owned Assets: Property, Plant and Equipment, Net, Excluding Capital Leased Assets [Abstract] Estimated useful lives Property, Plant and Equipment, Useful Life Owned assets, gross Property, Plant and Equipment, Gross, Excluding Capital Leased Assets Less: Accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Excluding Capital Leased Assets Owned assets, net Property, Plant and Equipment, Net, Excluding Capital Leased Assets Right-of-use assets under finance leases: Capital Leases, Balance Sheet, Assets by Major Class, Net [Abstract] Finance lease, right of use asset, gross Less: Accumulated depreciation and amortization Property and equipment, net Restricted Stock Restricted Stock [Member] Restricted Stock Units Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] Number, Outstanding, at Beginning Balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Number, Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Number, Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Number, Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Number, Outstanding, at Ending Balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted-Average Fair Value, Outstanding, at 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 Weighted-Average 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 Weighted-Average 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 Weighted-Average Fair Value, Forfeited (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 Weighted-Average Fair Value, Outstanding, at Ending Balance (in dollars per share) Units vested for which the underlying common stock is yet to be issued (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number Cash, Cash Equivalents and Restricted Cash Cash and Cash Equivalents Disclosure [Text Block] Schedule of Maturities of Long-term Debt Schedule of Maturities of Long-term Debt [Table Text Block] Other Assets Other Assets Disclosure [Text Block] Employee Stock Option Employee Stock Option [Member] Unrecognized compensation cost, unvested options Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Components of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Change in Plan Assets Schedule of Changes in Fair Value of Plan Assets [Table Text Block] 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] Number of Options, Outstanding, Beginning Balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Number of Options, Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Number of Options, Exercised (in shares) Number of Options, Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Number of Options, Outstanding, Ending Balance (in shares) Number of Options, Vested and exercisable at end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number 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] Weighted-Average Exercise Price, Outstanding, Beginning Balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Weighted-Average Exercise Price, Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Weighted-Average Exercise Price, Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Weighted-Average Exercise Price, Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Weighted-Average Exercise Price, Outstanding, Ending Balance (in dollars per share) Weighted Average Exercise Price, Vested and exercisable at end of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price 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] Aggregate Intrinsic Value, Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Aggregate Intrinsic Value, Exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Aggregate Intrinsic Value, Vested and exercisable at end of period Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value Weighted-Average Remaining Contractual Life Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted-Average Remaining Contractual Life, Vested and exercisable at end of period Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] General and administrative expenses General and Administrative Expense [Member] 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] Trade names and trademarks Trademarks and Trade Names [Member] Developed technology Developed Technology Rights [Member] Customer relationships Customer Relationships [Member] SCIO and Health Integrated SCIO and Health Integrated [Member] SCIO and Health Integrated [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Purchase consideration Business Combination, Consideration Transferred Utilized revolver credit facility to finance acquisition Proceeds from Lines of Credit Stock issued during period (in shares) Stock Issued During Period, Shares, Acquisitions Restricted common stock issued for acquisition of SCIO Stock Issued During Period, Value, Acquisitions Weighted average useful life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Acquisition related costs Business Combination, Acquisition Related Costs Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Amortization of actuarial (gain)/loss Defined Benefit Plan, Amortization of Gain (Loss) Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Cash and cash equivalents Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Restricted cash Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Restricted Cash Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Restricted Cash Accounts receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables Other current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other Property and equipment Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Other assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets Identifiable Intangible Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Current liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities Deferred tax liabilities, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities, Current Other non-current liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Net assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Total purchase consideration Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net Schedule of allocation of purchase price to assets acquired and liabilities assumed Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Schedule of Goodwill Schedule of Goodwill [Table Text Block] Schedule of indefinite lived Intangible Assets Schedule of Indefinite-Lived Intangible Assets [Table Text Block] Schedule of amortization of Intangible Assets Finite-lived Intangible Assets Amortization Expense [Table Text Block] Schedule of finite lived Intangible Assets useful lives Schedule Of Finite Lived Intangible Assets Useful Lives Table [Table Text Block] Schedule of finite lived intangible assets useful lives. Schedule of estimated future amortization of Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Summary of Other Income, net Interest and Other Income [Table Text Block] Numerator: Net Income (Loss) Attributable to Parent [Abstract] Denominators: Basic weighted average outstanding (in shares) Dilutive effect of share based awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted weighted average outstanding (in shares) Earnings per share attributable to ExlService Holdings Inc. stockholders: Earnings Per Share, Basic and Diluted [Abstract] Weighted average potentially dilutive considered anti-dilutive and not included in computing diluted earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Accrued Expenses and Other Current Liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Consulting Services Consulting Services [Member] Consulting Services [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Affiliated Entity Affiliated Entity [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Revenues from related party Accounts receivable from related party Accounts Receivable, Related Parties Related Party Transaction, Amounts of Transaction Related Party Transaction, Amounts of Transaction Debt outstanding Interest accrued Interest Payable Capital Structure Stockholders' Equity Note Disclosure [Text Block] Unrealized (loss)/gain on effective cash flow hedges, taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Realized gain on cash flow hedges, taxes Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Retirement benefits, taxes Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax Related Party Disclosures Related Party Transactions Disclosure [Text Block] Revenue Based PRSUs Revenue Based Performance Restricted Stock Units [Member] Revenue Based Performance Restricted Stock Units [Member] Market Condition Based PRSUs Market Condition Based Performance Restricted Stock Units [Member] Market Condition Based Performance Restricted Stock Units [Member] 2019 (April 1 - December 31) Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2020 Finite-Lived Intangible Assets, Amortization Expense, Next Rolling Twelve Months 2021 Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Two 2022 Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Three 2023 Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Four 2024 and thereafter Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Five Total Finite-Lived Intangible Assets, Net Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Forward Contracts Forward Contracts [Member] Derivatives in Cash Flow Hedging Relationships Foreign exchange contracts outstanding Derivative, Notional Amount Net derivative gains which could be reclassified into earnings within the next 12 months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Maximum outstanding term of cash flow hedges Maximum Length of Time Hedged in Cash Flow Hedge Schedule of Property and Equipment Property, Plant and Equipment [Table Text Block] 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] Cost of revenues Cost of Sales [Member] Selling and marketing expenses Selling and Marketing Expense [Member] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Stock-based compensation expenses Allocated Share-based Compensation Expense United States United Kingdom UNITED KINGDOM Rest of World Total Non-United States Non-US [Member] Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Cumulative foreign currency translation loss Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Unrealized gain/(loss) on cash flow hedges, net of taxes of $1,658 and $115, respectively AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax Retirement benefits, net of taxes of $56 and ($53), respectively Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Accumulated other comprehensive loss Unrealized gain on cash flow hedges, taxes Accumulated Other Comprehensive Income Loss Cumulative Changes In Net Gain Loss From Cash Flow Hedges Effect Tax Portion Accumulated Other Comprehensive Income Loss Cumulative Changes In Net Gain Loss From Cash Flow Hedges Effect Tax Portion Retirement benefits, taxes Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension And Other Post Retirement Plans, Tax Accumulated Other Comprehensive Income (Loss), Defined Benefit Pension And Other Post Retirement Plans, Tax Leases Lessee, Operating Leases [Text Block] Leases Lessee, Finance Leases [Text Block] Revenues, net Revenue from Contract with Customer [Text Block] Other Current Assets Other Current Assets [Text Block] Restricted Stock and Restricted Stock Units Restricted Stock and Restricted Stock Units [Member] Restricted Stock and Restricted Stock Units [Member] Summary of Fair Value of Foreign Currency Exchange Contracts Schedule of Foreign Exchange Contracts, Statement of Financial Position [Table Text Block] Summary of Effect of Foreign Currency Exchange Contracts on Consolidated Statements of Income Derivative Instruments, Gain (Loss) [Table Text Block] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] Revenue recognition contract terms Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Explanation Payment terms Contract With Customer, Payment Terms Contract With Customer, Payment Terms Value of unsatisfied performance obligations not disclosed for contracts (less than) Revenue, Performance Obligation, Unsatisfied, Contract Length Of Time Revenue, Performance Obligation, Unsatisfied, Contract Length Of Time Deferred rent Deferred Rent Credit, Current Operating lease liabilities Assets and Liabilities Measured at Fair Value Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Summary of Other Non-Current Liabilities Other Noncurrent Liabilities [Table Text Block] Schedule of supplemental balance sheet information Schedule Of Leases In Statement Of Financial Position [Table Text Block] Schedule Of Leases In Statement Of Financial Position [Table Text Block] Schedule of components of lease cost Lease, Cost [Table Text Block] Schedule of supplemental cash flow informaton related to leases Schedule Of Supplemental Cash Flow And Other Information, Leases [Table Text Block] Schedule of Statement of Cash Flows, Supplemental Disclosures [Table Text Block] Schedule of maturities of lease liabilities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Schedule of maturities of lease liabilities Finance Lease, Liability, Maturity [Table Text Block] Schedule of future minimum lease payments for capital leases Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Schedule of future minimum rental payments for operating leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Fair value of convertible notes Interest and dividend income Investment Income, Interest and Dividend Gain on sale and mark-to-market of mutual funds Gain (Loss) on Investments Others, net Other Miscellaneous Nonoperating Income (Expense) Other Miscellaneous Nonoperating Income (Expense) Other income, net Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Leasehold benefits Leasehold Benefits [Member] Leasehold benefits. Non-compete agreements Noncompete Agreements [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Finite-lived intangible assets, gross carrying amount Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Accumulated Impairment Total intangible assets, gross carrying amount Intangible Assets, Gross (Excluding Goodwill) Total intangible assets, net carrying amount Indefinite lived intangible assets [Abstract] Indefinite lived intangible assets [Abstract] Indefinite lived intangible assets [Abstract] Trade names and trademarks Indefinite-lived Intangible Assets (Excluding Goodwill) Impairment of intangible assets Impairment of Intangible Assets, Finite-lived Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Customer relationships Leasehold benefits Developed technology Non-compete agreements Trade names and trademarks (Finite lived) Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Weighted average life of intangible assets Finite-Lived Intangible Assets, Remaining Amortization Period Fair Value Measurements Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Cost Capitalized Computer Software, Gross Less : Accumulated amortization Capitalized Computer Software, Accumulated Amortization Internally developed software, net Capitalized Computer Software, Net Amortization expense Capitalized Computer Software, Amortization Purchase commitments, net of advances Purchase Commitment, Remaining Minimum Amount Committed Export-oriented units established, percentage Export Oriented Units Established Percentage Export oriented units established percentage. Aggregate disputed amount amount related to transfer pricing and permanent establishment Aggregate Disputed Amount Related to Transfer Pricing and Permanent Establishment Aggregate disputed amount related to transfer pricing and permanent establishment Litigation, settlement amount Litigation Settlement, Amount Awarded to Other Party Settlement payments made during the period Loss Contingency Accrual, Payments Total bank guarantees and deposits in respect of contingencies Total Bank Guarantees And Deposits In Respect Of Contingencies Total Bank Guarantees and Deposits in Respect of Contingencies Amounts paid as deposits in respect of contingencies Amounts Paid As Deposits In Respect Of Contingencies Amounts paid as deposits in respect of Contingencies. Bank guarantee issued Bank Guarantee Issued Bank Guarantee Issued Investment in Equity Affiliate Equity Method Investments and Joint Ventures Disclosure [Text Block]