Business Combination, Goodwill And Intangible Assets Disclosure [Abstract] Business Combination, Goodwill And Intangible Assets Disclosure [Abstract] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [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] Customer relationships Customer Relationships [Member] Leasehold benefits Leasehold Benefits [Member] Leasehold benefits. Developed technology Developed Technology Rights [Member] Non-compete agreements Noncompete Agreements [Member] Trade names and trademarks (Finite lived) Trademarks and Trade Names [Member] 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 Leases [Abstract] Rent expense Operating Leases, Rent Expense, Net Cancelable and non-cancelable operating leases Deferred Rent Credit Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Customer relationships Developed technology Trade names and trademarks 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] Business Acquisition [Line Items] Business Acquisition [Line Items] Purchase consideration Business Combination, Consideration Transferred Maximum contingent consideration Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High Contingent cash consideration Business Combination, Contingent Consideration, Liability Weighted average useful life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Liabilities, Noncurrent [Abstract] Summary of Other Non-Current Liabilities Other Noncurrent Liabilities [Table Text Block] Earnings Per Share [Abstract] Numerator: Net Income (Loss) Attributable to Parent [Abstract] Net income Net Income (Loss) Attributable to Parent Denominators: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic weighted average outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic 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) Weighted Average Number of Shares Outstanding, Diluted Earnings per share attributable to ExlService Holdings Inc. stockholders: Earnings Per Share, Basic and Diluted [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted 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 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, 2018 Defined Benefit Plan, Fair Value of Plan Assets 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 June 30, 2018 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 Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net (Gain)/loss recognized in unaudited consolidated statements of income Foreign Currency Transaction Gain (Loss), before Tax Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Equity Method Investments and Joint Ventures [Abstract] Investment in equity affiliate Equity Method Investments and Joint Ventures Disclosure [Text Block] Segment Reporting [Abstract] Segment and Geographical Information Segment Reporting Disclosure [Text Block] Property, Plant and Equipment [Abstract] Schedule of Property and Equipment Property, Plant and Equipment [Table 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] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Event Subsequent Events [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] Earnings Per Share Earnings Per Share [Text Block] 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] 2014 and 2017 Repurchase Program Two Thousand Fourteen and Two Thousand Seventeen Repurchase Program [Member] Two Thousand Fourteen and 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 by board of directors up to 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 Authorized increase in repurchase amount, 2019 Stock Repurchase Program, Authorized Increase in Repurchase Amount Per Period, Year Three Stock Repurchase Program, Authorized Increase in Repurchase Amount Per Period, Year Three 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 Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies 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] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Retained Earnings Retained Earnings [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Impact of adoption of Topic 606 Accounting Standards Update 2014-09 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Cumulative effect Cumulative Effect of New Accounting Principle in Period of Adoption 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 Capitalized contract acquisition costs, amount amortized Capitalized Contract Cost, Amortization Deferred costs, contract fulfillment Amount of Deferred Costs Related to Long-term Contracts Schedule of Goodwill [Table] Schedule of Goodwill [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Insurance Insurance [Member] Insurance [Member] Healthcare Healthcare [Member] Healthcare [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] Goodwill [Roll Forward] Goodwill [Roll Forward] Beginning Balance Goodwill Acquisitions Goodwill, Acquired During Period Currency translation adjustments Goodwill, Foreign Currency Translation Gain (Loss) Measurement period adjustments Goodwill, Purchase Accounting Adjustments Ending Balance Measurement period adjustments, intangible assets acquired and earn-out Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles, Net Of Adjustment, Contingent Liability Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles, Net Of Adjustment, Contingent Liability Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Schedule of Other Assets Schedule of Other Assets [Table Text Block] Other Income and Expenses [Abstract] Other Income, net Interest and Other Income [Text Block] Derivatives Designated as Hedging Instruments Cost of revenues Cost of Services 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 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] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Employee Stock Option Employee Stock Option [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] 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] Effect of Retrospective Presentation Change Related to the Net Periodic Cost of Defined Benefit Pension Plans on Consolidated Statements of Income Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Change in Plan Assets Schedule of Changes in Fair Value of Plan Assets [Table Text Block] Capital Structure Stockholders' Equity Note Disclosure [Text Block] Lease deposits Security Deposit Derivative instruments Derivative Asset Deposits with statutory authorities Deposit Assets Term deposits Time Deposits, at Carrying Value Others Other Assets, Miscellaneous Other assets Other Assets 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 Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Adjustments to reconcile net income to net cash provided 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 (gain)/loss Foreign Currency Transaction Gain (Loss), Unrealized Deferred income tax expense/(benefit) Deferred Income Tax Expense (Benefit) Allowances for doubtful accounts receivable Provision for Doubtful Accounts Loss from equity-method investment Income (Loss) from Equity Method Investments 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 Accounts payable Increase (Decrease) in Accounts Payable Deferred revenue Increase (Decrease) in Customer Contract Liability Increase (Decrease) in Customer Contract 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 Advance income tax, net Increase (Decrease) in Income Taxes Payable Other assets Increase (Decrease) in Other Operating Assets Net cash provided by 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 provided by/(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 capital 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 Acquisition of treasury stock Payments for Repurchase of Common Stock Proceeds from exercise of stock options Proceeds from Stock Options Exercised Net cash 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, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents, and restricted cash at end of period Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] 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] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] 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 Assets under capital leases: Capital Leases, Balance Sheet, Assets by Major Class, Net [Abstract] Capital leased assets, gross Capital Leased Assets, Gross Less: Accumulated depreciation and amortization Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation Assets under capital leases, net Capital Leases, Balance Sheet, Assets by Major Class, Net Property and equipment, net Property, Plant and Equipment, Net 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) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period 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, Beginning Balance 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, Outstanding, Ending Balance 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 Statement of Comprehensive Income [Abstract] Unrealized (loss)/gain on effective cash flow hedges, taxes Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Realized gain on cash flow hedges, taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax Retirement benefits, taxes Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax Interest and dividend income Investment Income, Interest and Dividend Gain on sale of mutual funds Gain (Loss) on Investments Others, net Other Miscellaneous Nonoperating Income (Expense) Other Miscellaneous Nonoperating Income (Expense) Other income, net Other Nonoperating Income (Expense) 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] 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] United States UNITED STATES United Kingdom UNITED KINGDOM Rest of World Rest Of World [Member] Rest of World. Total Non-United States Non-US [Member] Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Revenues, net Revenue from Contract with Customer, Excluding Assessed Tax Schedule of Accrued Expenses and Other Current Liabilities Schedule of Accrued Liabilities [Table Text Block] Accounting Policies [Abstract] Summary of Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Business Combinations, Goodwill and Intangible Assets Disclosure [Abstract] Business Combinations, Goodwill and Intangible Assets Disclosure [Abstract] Tangible Assets Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Tangible Assets Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Tangible Assets Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Identifiable Intangible Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Goodwill Total purchase price Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net Allocation of Purchase Price to Assets Acquired and Liabilities Assumed Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Summary of Company's Goodwill Schedule of Goodwill [Table Text Block] Schedule of Indefinite-Lived Intangible Assets Schedule of Indefinite-Lived Intangible Assets [Table Text Block] Schedule of Finite Lived Intangibles Assets and Weighted Average Life Schedule of Finite-Lived Intangible Assets [Table Text Block] Amortization of Intangible Assets Finite-lived Intangible Assets Amortization Expense [Table Text Block] Estimated Future Amortization of Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Schedule of Indefinite-Lived Intangible Assets [Table] Schedule of Indefinite-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] Indefinite-lived Intangible Assets [Line Items] Indefinite-lived Intangible Assets [Line Items] Trade names and trademarks Indefinite-Lived Intangible Assets (Excluding Goodwill) Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Leasehold benefits Non-compete agreements 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 Total Finite-Lived Intangible Assets, Net Total intangible assets, gross carrying amount Intangible Assets, Gross (Excluding Goodwill) Total intangible assets, net carrying amount Intangible Assets, Net (Excluding Goodwill) 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 Leases Leases of Lessee Disclosure [Text Block] 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 Cash and Cash Equivalents, at Carrying Value Restricted cash (current) Restricted Cash, Current Restricted cash (non-current) Restricted Cash, Noncurrent Total cash, cash equivalents and restricted cash shown in the statement of cash flows Fair Value Disclosures [Abstract] Fair value of earn-out consideration 2019 Finite-Lived Intangible Assets, Amortization Expense, Next Rolling Twelve Months 2020 Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Two 2021 Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Three 2022 Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Four 2023 Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Five 2024 and thereafter Finite-Lived Intangible Assets, Amortization Expense, Rolling after Year Five Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Revenue from External Customers by Products and Services [Table] Revenue from External Customers by Products and Services [Table] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [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] Cost of revenues(1) Cost of Services, Excluding Depreciation, Depletion, and Amortization Gross profit Gross Profit Operating expenses Operating Expenses Foreign exchange gain, interest expense and other income, net Nonoperating Income (Expense) Income tax expense Income Tax Expense (Benefit) Net income attributable to ExlService Holdings, Inc. stockholders Number of operating segments, industry focused Number of Operating Segments, Industry Focused Number of Operating Segments, Industry Focused Number of capability operating segments Number of Operating Segments, Finance and Accounting Services Number of Operating Segments, Finance and Accounting Services Related Party Transactions [Abstract] Related Party Disclosures Related Party Transactions Disclosure [Text Block] 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 Total minimum lease payments Capital Leases, Future Minimum Payments Due Less: amount representing 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 India INDIA United States Philippines PHILIPPINES Rest of World Property and equipment, net Stock Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] 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, finance and accounting 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 Assets and Liabilities Measured at Fair Value Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Revenue from related party Revenue from Related Parties Accounts receivable from related party Accounts Receivable, Related Parties Derivative instruments Derivative Asset, Current Advances to suppliers Prepaid Supplies Receivables from statutory authorities Service Taxes Receivable, Current Service Taxes Receivable, Current Others Other Assets, Miscellaneous, Current Other current assets Other Assets, Current 2015 Stock Options Plan Two Thousand Fifteen Stock Options Plan [Member] Two Thousand Fifteen Stock Options Plan [Member] Number available for grant (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Revenues, net Revenue from Contract with Customer [Text Block] Accrued expenses and other current liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Summary of Other Income, net Interest and Other Income [Table Text Block] Cost Capitalized Computer Software, Gross Less : Accumulated amortization Capitalized Computer Software, Accumulated Amortization Net Capitalized Computer Software, Net 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 [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [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] Money market and 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 Fair value of earn-out consideration Nonfinancial Liabilities Fair Value Disclosure Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Amortization expense Amortization of Intangible Assets Cash, Cash Equivalents and Restricted Cash Cash and Cash Equivalents Disclosure [Text Block] 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 Debt Disclosure [Abstract] Borrowings Debt Disclosure [Text Block] Document And Entity Information [Abstract] Document and entity information. 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 Type Document Type 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 Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Property and Equipment, net Property, Plant and Equipment 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] 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, Addition due to achievement of higher-than-target performance Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additions Due to Achievement in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additions Due to Achievement 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, Addition due to achievement of higher-than-target performance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additions due to Achievement in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additions due to Achievement 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) 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 and thereafter Operating Leases, Future Minimum Payments, Due in Rolling after Year Five Total operating lease payments Operating Leases, Future Minimum Payments Due Contracts with Customer, Receivables and Liabilities Contract with Customer, Asset and Liability [Table Text Block] Income Statement [Abstract] Revenues, net Cost of revenues Operating expenses: Operating Expenses [Abstract] General and administrative expenses Selling and marketing expenses Depreciation and amortization Total operating expenses Income from operations Operating Income (Loss) Foreign exchange gain, net Interest expense Interest Expense Other income, net Income before income tax expense Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Earnings per share attributable to ExlService Holdings, Inc. stockholders: Weighted-average number of shares used in computing earnings per share attributable to ExlService Holdings, Inc. stockholders: Basic (in shares) Diluted (in shares) Income tax (benefit) expense Effective tax rate, current income tax expense (benefit) Effective Income Tax Rate Reconciliation, Percent Tax Adjustments, Settlements, and Unusual Provisions Tax Adjustments, Settlements, and Unusual Provisions 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) Excess tax benefits, stock awards Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Transition tax obligation Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Liability Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Liability Transition tax, income tax expense (benefit) Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Income Tax Expense Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Income Tax Expense Provisional adjustments associated with the corporate rate change Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Expense (Benefit) Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Expense (Benefit) 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 expense 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 Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Cost of revenues Cost of Sales [Member] General and administrative expenses General and Administrative Expense [Member] Selling and marketing expenses Selling and Marketing Expense [Member] Other income, net Other Nonoperating Income (Expense) [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Previously reported Scenario, Previously Reported [Member] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Net periodic benefit cost Net periodic benefit cost, effect of change, higher/ (lower) Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Increase (Decrease) Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Increase (Decrease) Line of Credit Facility [Table] Line of Credit Facility [Table] 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] Credit Facility Credit Facility [Member] Credit Facility [Member] New Credit Agreement New Credit Agreement [Member] New Credit Agreement [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] 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. Interest rate Line of Credit Facility, Interest Rate During Period 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 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, current Line of Credit, Current Outstanding debt, noncurrent Long-term Line of Credit, Noncurrent Debt issuance costs Payments of Debt Issuance Costs Unamortized debt issuance costs Debt Issuance Costs, Net Structured payable Long-term Debt Current portion of long-term borrowings Long-term Debt, Current Maturities Long term borrowings Long-term Debt, Excluding Current Maturities Debt instrument, covenant, interest coverage ratio, minimum Debt Instrument, Covenant, Interest Coverage Ratio, Minimum Debt Instrument, Covenant, Interest Coverage Ratio, Minimum Debt instrument, covenant, leverage ratio, maximum Debt Instrument, Covenant, Leverage Ratio, Maximum Debt Instrument, Covenant, Leverage Ratio, Maximum Other non-current liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Noncurrent [Text Block] 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 Other non-current liabilities Other Liabilities, Noncurrent Non-current liabilities Liabilities, Other than Long-term Debt, Noncurrent Subsequent Event [Table] Subsequent Event [Table] Fresh-Start Adjustments [Axis] Fresh-Start Adjustments [Axis] Type of Fresh-Start Adjustment [Domain] Type of Fresh-Start Adjustment [Domain] Exchange of Stock for Stock [Member] Exchange of Stock for Stock [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] SCIOInspire Holdings, Inc. SCIOInspire Holdings, Inc. [Member] SCIOInspire Holdings, Inc. [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Business acquisition, equity interest issued or issuable, value assigned Business Acquisition, Equity Interest Issued or Issuable, Value Assigned Stock issued during period, shares, new issues Stock Issued During Period, Shares, New Issues Line of credit facility, increase (decrease), net Line of Credit Facility, Increase (Decrease), Net Cumulative foreign currency translation (loss) Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Unrealized (loss)/gain on cash flow hedges, net of taxes of ($657) and $4,918, respectively Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax Retirement benefits, net of taxes of ($76) and ($74), respectively Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax 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 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] 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, sales of services Revenue from Contract with Customer [Policy Text Block] Revenue from Contract with Customer [Policy Text Block] Recent Accounting Pronouncements and Recently Adopted Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Other current assets Other Current Assets [Text Block] 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. Transfer pricing issues starting period Transfer Pricing Issues Starting Period Transfer Pricing Issues Starting Period Transfer pricing issues ending period Transfer Pricing Issues Ending Period Transfer Pricing Issues Ending Period Permanent establishment issues starting period Transfer Pricing Establishment Issues Starting Period Transfer Pricing Establishment Issues Starting Period Permanent establishment issues ending period Transfer Pricing Establishment Issues Ending Period Transfer Pricing Establishment Issues Ending Period 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 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 Litigation settlement, amount Litigation Settlement, Amount Awarded to Other Party Other comprehensive (loss)/income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Unrealized (loss)/gain on effective cash flow hedges, net of taxes ($3,573), $1,536, ($4,373) and $3,580, respectively Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Foreign currency translation (loss)/gain 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 ($426), ($607), ($1,202) and ($891), respectively(1) Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Retirement benefits, net of taxes ($3), $40, ($2) and $47, respectively(2) Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Total other comprehensive (loss)/income Other Comprehensive Income (Loss), Net of Tax Total comprehensive (loss)/income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest 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] 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 Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Fair Value Measurements Fair Value, Measurement Inputs, Disclosure [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 Total current assets Assets, Current Restricted cash Deferred taxes, net Deferred Tax Assets, Net Intangible assets, net Other assets Other Assets, Noncurrent Equity Method Investments Equity Method Investments Total assets Assets Liabilities and equity Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Deferred revenue Contract with Customer, Liability, Current Accrued employee costs Employee-related Liabilities, Current Accrued expenses and other current liabilities Current portion of capital lease obligations Total current liabilities Liabilities, Current Capital lease obligations, less current portion Income taxes payable Accrued Income Taxes, Noncurrent Other non-current liabilities Total liabilities Liabilities Commitments and contingencies (Refer to Note 25) 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, 37,583,160 shares issued and 34,288,314 shares outstanding as of June 30, 2018 and 36,790,751 shares issued and 33,888,733 shares outstanding as of December 31, 2017 Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Total including shares held in treasury Stockholders Equity Including Shares Held In Treasury Total stockholders' equity including shares held in treasury. Less: 3,294,846 shares as of June 30, 2018 and 2,902,018 shares as of December 31, 2017, 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 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 Restricted Stock and Restricted Stock Units Restricted Stock and Restricted Stock Units [Member] Restricted Stock and Restricted Stock Units [Member] Performance Based Stock Awards Performance Based Stock Awards [Member] Performance Based Stock Awards [Member] Costs Related to Company's Stock-Based Compensation Plan Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Stock Based Compensation Stock Option Activity Share-based Compensation, Stock Options, Activity [Table Text Block] Stock Activity Under Company's Stock Plans Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Schedule of Other Current Assets Schedule of Other Current Assets [Table Text Block] Derivatives and Hedge Accounting Derivative Instruments and Hedging Activities Disclosure [Text Block] 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 Typical length of contract Contract With Customer, Contract Term Contract With Customer, Contract Term 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 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 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] 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 Future Minimum Lease Payments under Capital Leases Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Future Minimum Lease Payments under Operating Lease Agreements Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Rent Expense Schedule of Rent Expense [Table Text Block] Schedule of Deferred Rent Schedule of Other Assets and Other Liabilities [Table Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Impact of adoption of ASU 2016-09 Accounting Standards Update 2016-09 [Member] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive (Loss) 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 Adjustments for new accounting pronouncements Adjusted equity balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance Stock issued on exercise/vesting of equity awards (in shares) Stock issued on exercise/vesting of equity awards 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 loss Ending balance (in shares) Ending balance Depreciation and amortization expense Depreciation Depreciation and Amortization Depreciation And Amortization [Member] Depreciation And Amortization [Member] Effect of the foreign exchange gains upon settlement of cash flow hedges Gain (Loss) on Hedging Activity Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Accounts receivable, net Contract liabilities Contract with Customer, Liability [Abstract] Deferred revenue (advance payments portion) Contract with Customer, Liability Other Assets Other Assets Disclosure [Text Block]