Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies (a) Basis of Preparation and Principles of Consolidation The unaudited interim consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“US GAAP”) for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by US GAAP for annual financial statements and therefore should be read in conjunction with the audited consolidated financial statements and footnotes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016. The unaudited interim consolidated financial statements reflect all adjustments (of a normal and recurring nature) that management considers necessary for a fair presentation of such statements for the interim periods presented. The unaudited consolidated statements of income for the interim periods presented are not necessarily indicative of the results for the full year or for any subsequent period. The accompanying unaudited consolidated financial statements include the financial statements of ExlService Holdings and all of its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Non-controlling interest is the equity in a subsidiary not attributable, directly or indirectly, to the parent and it represents the minority partner’s interest in the operations of ExlService Colombia S.A.S. Non-controlling interest consists of the amount of such interest at the date of obtaining control over the subsidiary, and the non-controlling interest's share of changes in equity since that date. The non-controlling interest in the operations for all the periods presented were insignificant and are included under general and administrative expenses in the unaudited consolidated statements of income. (b) Use of Estimates The preparation of the unaudited consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited consolidated financial statements and the unaudited consolidated statements of income during the reporting period. Although these estimates are based on management’s best assessment of the current business environment, actual results may be different from those estimates. The significant estimates and assumptions that affect the financial statements include, but are not limited to, allowance for doubtful receivables, recoverability of service tax receivables, assets and obligations related to employee benefit plans, deferred tax valuation allowances, income-tax uncertainties and other contingencies, valuation of derivative financial instruments, assumptions used to calculate stock-based compensation expense, depreciation and amortization periods, purchase price allocation, recoverability of long-term assets including goodwill and intangibles, and estimates to complete fixed price contracts. (c) Share-Based Compensation In March 2016, the FASB issued ASU No. 2016-09, Compensation - Stock Compensation (Topic 718). ASU No. 2016-09 identifies areas for simplification involving several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, an option to recognize gross stock compensation expense with actual forfeitures recognized as they occur, as well as certain classifications on the Statement of Cash Flows. The amendments are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. The Company adopted this ASU effective January 1, 2017. The following summarizes the effects of the adoption on the Company's unaudited consolidated financial statements: Income taxes - Upon adoption of this standard, all excess tax benefits and tax deficiencies are recognized as income tax expense or benefit in the income statement. The tax effects of exercised or vested awards are treated as discrete items in the reporting period in which they occur. The Company also recognizes excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. As a result, the Company recognized discrete adjustments to income tax expense for the three months ended March 31, 2017, in the amount of $2,057, related to excess tax benefits. No adjustment is recorded for any windfall benefits previously recorded in APIC. Forfeitures - Prior to adoption, share-based compensation expense was recognized on a straight line basis, net of estimated forfeitures, such that expense was recognized only for share-based awards that are expected to vest. A forfeiture rate was estimated annually and revised, if necessary, in subsequent periods if actual forfeitures differed from initial estimates. Upon adoption, the Company will no longer apply a forfeiture rate and instead will account for forfeitures as they occur. The Company has applied the modified retrospective adoption approach as of January 1, 2017 and has recognized a cumulative-effect adjustment to reduce additional paid-in-capital of $5,999 and retained earnings of $4,546 (net of deferred tax effect of $1,453). Statements of Cash Flows - The Company historically accounted for excess tax benefits on the Statement of Cash Flows as a financing activity. Upon adoption of this standard, excess tax benefits are classified along with other income tax cash flows as an operating activity. The Company has elected to adopt this portion of the standard on a prospective basis beginning in 2017 and accordingly prior periods have not been adjusted. Earnings Per Share - The Company uses the treasury stock method to compute diluted earnings per share, unless the effect would be anti-dilutive. The Company excluded the excess tax benefits from the assumed proceeds available to repurchase shares in the computation of diluted earnings per share. Upon adoption, no other aspects of ASU 2016-09 had an effect on the Company's unaudited consolidated financial statements or related footnote disclosures. (d) Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09, “Revenue from Contracts with Customers”. The new standard is effective for reporting periods beginning after December 15, 2017 and early adoption is not permitted. The comprehensive new standard will supersede existing revenue recognition guidance and require revenue to be recognized when promised goods or services are transferred to customers in amounts that reflect the consideration to which the Company expects to be entitled in exchange for those goods or services. Adoption of the new rules could affect the timing of revenue recognition for certain transactions of the Company. ASU 2014-09 is effective for the Company in the first quarter of fiscal 2018 using either one of two methods: (i) retrospectively to each prior reporting period presented with the option to elect certain practical expedients as defined within ASU 2014-09; or (ii) retrospectively with the cumulative effect of initially applying ASU 2014-09 recognized at the date of initial application and providing certain additional disclosures as defined per ASU 2014-09. The Company is evaluating the impact of the standard update. The ultimate impact on revenue resulting from the application of the new standard will be subject to assessments that are dependent on many variables, including, but not limited to, the terms of the contractual arrangements and the mix of business. Upon adoption, we expect there to be a change in the manner that variable consideration in certain revenue arrangements is recognized from the current practice of recognizing such revenue as the services are performed and the variable consideration is earned to estimating the achievability of the variable conditions when we begin delivering services and recognizing that amount over the contractual period. The Company also expects a change in the manner that it recognizes certain incremental and fulfillment costs from expensing them as incurred to deferring and recognizing them over the contractual period. The Company continues to evaluate the available transition methods and its contractual arrangements. The Company's considerations include, but are not limited to, the comparability of its financial statements and the comparability within its industry from application of the new standard to its contractual arrangements. The Company plans to select a transition method by the second half of 2017. We have established an implementation team to implement the standard update related to the recognition of revenue from contracts with customers. The Company continues to evaluate the changes to accounting system and processes, and additional disclosure requirements that may be necessary. In March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net). ASU 2016-08 clarifies the implementation guidance on principal versus agent considerations. The guidance includes indicators to assist an entity in determining whether it controls a specified good or service before it is transferred to the customers. The amendments are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company is currently evaluating the impact that the adoption of this guidance will have on its consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASU 2016-02 requires the identification of arrangements that should be accounted for as leases by lessees. In general, for lease arrangements exceeding a twelve month term, these arrangements must now be recognized as assets and liabilities on the balance sheet of the lessee. Under ASU 2016-02, a right-of-use asset and lease obligation will be recorded for all leases, whether operating or financing, while the income statement will reflect lease expense for operating leases and amortization/interest expense for financing leases. The balance sheet amount recorded for existing leases at the date of adoption of ASU 2016-02 must be calculated using the applicable incremental borrowing rate at the date of adoption. In addition, ASU 2016-02 requires the use of the modified retrospective method, which will require adjustment to all comparative periods presented in the consolidated financial statements. The new guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company is currently evaluating the impact that the adoption of this guidance will have on its consolidated financial statements and the implementation approach to be used. In June 2016, FASB issued ASU 2016-13, Financial Instruments - Credit Losses, which require a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. The allowance for credit losses is a valuation account that is to be deducted from the amortized cost basis of the financial asset(s) to present the net carrying value at the amount expected to be collected on the financial asset. The new guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The amendment should be applied through a modified retrospective approach. Early adoption as of the fiscal years beginning after December 15, 2018 is permitted. The adoption of ASU 2016-13 is not expected to have a material effect on its consolidated financial statements. In August 2016, FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments. The amendments apply to all entities that are required to present a Statement of Cash Flows under Topic 230. The amendments are an improvement to GAAP because they provide guidance for each of the eight issues, thereby reducing the current and potential future diversity in practice. The amendments are effective for fiscal years beginning after December 15, 2017 and interim periods within those annual periods and should be applied using a retrospective transition method to each period presented. The Company does not expect the adoption of this ASU to have a material effect on its financial position or results of operations. In November 2016, FASB issued ASU 2016-18, Statement of Cash Flows - Restricted cash. The amendments apply to all entities that have restricted cash or restricted cash equivalents and are required to present a Statement of Cash Flows under Topic 230. The amendments in this update require that a Statement of Cash Flows should explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. The amendments are effective for fiscal years beginning after December 15, 2017 and interim periods within those annual periods. Early adoption is permitted with an adjustment reflected as of the beginning of the fiscal year in which the amendment is adoption. The Company does not expect the adoption of this ASU to have a material effect on its financial position or results of operations. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (Topic 350), which eliminates Step 2 from the goodwill impairment test. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 is effective for annual and interim periods in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed after January 1, 2017 and should be applied prospectively. The Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements. In March, 2017, FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost. The ASU amends ASC 715, Compensation — Retirement Benefits, to require employers that present a measure of operating income in their statement of income to include only the service cost component of net periodic pension cost and net periodic post-retirement benefit cost in operating expenses (together with other employee compensation costs). The other components of net benefit cost, including amortization of prior service cost/credit, and settlement and curtailment effects, are to be included in non-operating expenses. The update also stipulates that only the service cost component of net benefit cost is eligible for capitalization. The amendments are effective for fiscal years beginning after December 15, 2017 and interim periods within those annual periods. Early adoption is permitted as of the beginning of an annual period. The Company is currently evaluating the impact that the adoption of this guidance will have on its consolidated financial statements.

Summary of Significant Accounting Policies

(a) Basis of Preparation and Principles of Consolidation

The unaudited interim consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“US GAAP”) for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by US GAAP for annual financial statements and therefore should be read in conjunction with the audited consolidated financial statements and footnotes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016.

The unaudited interim consolidated financial statements reflect all adjustments (of a normal and recurring nature) that management considers necessary for a fair presentation of such statements for the interim periods presented. The unaudited consolidated statements of income for the interim periods presented are not necessarily indicative of the results for the full year or for any subsequent period.

The accompanying unaudited consolidated financial statements include the financial statements of ExlService Holdings and all of its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Non-controlling interest is the equity in a subsidiary not attributable, directly or indirectly, to the parent and it represents the minority partner’s interest in the operations of ExlService Colombia S.A.S. Non-controlling interest consists of the amount of such interest at the date of obtaining control over the subsidiary, and the non-controlling interest's share of changes in equity since that date. The non-controlling interest in the operations for all the periods presented were insignificant and are included under general and administrative expenses in the unaudited consolidated statements of income.

(b) Use of Estimates

The preparation of the unaudited consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the unaudited consolidated financial statements and the unaudited consolidated statements of income during the reporting period. Although these estimates are based on management’s best assessment of the current business environment, actual results may be different from those estimates. The significant estimates and assumptions that affect the financial statements include, but are not limited to, allowance for doubtful receivables, recoverability of service tax receivables, assets and obligations related to employee benefit plans, deferred tax valuation allowances, income-tax uncertainties and other contingencies, valuation of derivative financial instruments, assumptions used to calculate stock-based compensation expense, depreciation and amortization periods, purchase price allocation, recoverability of long-term assets including goodwill and intangibles, and estimates to complete fixed price contracts.

In March 2016, the FASB issued ASU No. 2016-09, Compensation - Stock Compensation (Topic 718). ASU No. 2016-09 identifies areas for simplification involving several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, an option to recognize gross stock compensation expense with actual forfeitures recognized as they occur, as well as certain classifications on the Statement of Cash Flows. The amendments are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. The Company adopted this ASU effective January 1, 2017. The following summarizes the effects of the adoption on the Company's unaudited consolidated financial statements:

Income taxes - Upon adoption of this standard, all excess tax benefits and tax deficiencies are recognized as income tax expense or benefit in the income statement. The tax effects of exercised or vested awards are treated as discrete items in the reporting period in which they occur. The Company also recognizes excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. As a result, the Company recognized discrete adjustments to income tax expense for the three months ended March 31, 2017, in the amount of $2,057, related to excess tax benefits. No adjustment is recorded for any windfall benefits previously recorded in APIC.

Forfeitures - Prior to adoption, share-based compensation expense was recognized on a straight line basis, net of estimated forfeitures, such that expense was recognized only for share-based awards that are expected to vest. A forfeiture rate was estimated annually and revised, if necessary, in subsequent periods if actual forfeitures differed from initial estimates. Upon adoption, the Company will no longer apply a forfeiture rate and instead will account for forfeitures as they occur. The Company has applied the modified retrospective adoption approach as of January 1, 2017 and has recognized a cumulative-effect adjustment to reduce additional paid-in-capital of $5,999 and retained earnings of $4,546 (net of deferred tax effect of $1,453).

Statements of Cash Flows - The Company historically accounted for excess tax benefits on the Statement of Cash Flows as a financing activity. Upon adoption of this standard, excess tax benefits are classified along with other income tax cash flows as an operating activity. The Company has elected to adopt this portion of the standard on a prospective basis beginning in 2017 and accordingly prior periods have not been adjusted.

Earnings Per Share - The Company uses the treasury stock method to compute diluted earnings per share, unless the effect would be anti-dilutive. The Company excluded the excess tax benefits from the assumed proceeds available to repurchase shares in the computation of diluted earnings per share.

Upon adoption, no other aspects of ASU 2016-09 had an effect on the Company's unaudited consolidated financial statements or related footnote disclosures.

(d) Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2014-09, “Revenue from Contracts with Customers”. The new standard is effective for reporting periods beginning after December 15, 2017 and early adoption is not permitted. The comprehensive new standard will supersede existing revenue recognition guidance and require revenue to be recognized when promised goods or services are transferred to customers in amounts that reflect the consideration to which the Company expects to be entitled in exchange for those goods or services. Adoption of the new rules could affect the timing of revenue recognition for certain transactions of the Company. ASU 2014-09 is effective for the Company in the first quarter of fiscal 2018 using either one of two methods: (i) retrospectively to each prior reporting period presented with the option to elect certain practical expedients as defined within ASU 2014-09; or (ii) retrospectively with the cumulative effect of initially applying ASU 2014-09 recognized at the date of initial application and providing certain additional disclosures as defined per ASU 2014-09.

The Company is evaluating the impact of the standard update. The ultimate impact on revenue resulting from the application of the new standard will be subject to assessments that are dependent on many variables, including, but not limited to, the terms of the contractual arrangements and the mix of business. Upon adoption, we expect there to be a change in the manner that variable consideration in certain revenue arrangements is recognized from the current practice of recognizing such revenue as the services are performed and the variable consideration is earned to estimating the achievability of the variable conditions when we begin delivering services and recognizing that amount over the contractual period. The Company also expects a change in the manner that it recognizes certain incremental and fulfillment costs from expensing them as incurred to deferring and recognizing them over the contractual period.

The Company continues to evaluate the available transition methods and its contractual arrangements. The Company's considerations include, but are not limited to, the comparability of its financial statements and the comparability within its industry from application of the new standard to its contractual arrangements. The Company plans to select a transition method by the second half of 2017. We have established an implementation team to implement the standard update related to the recognition of revenue from contracts with customers. The Company continues to evaluate the changes to accounting system and processes, and additional disclosure requirements that may be necessary.

In March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net). ASU 2016-08 clarifies the implementation guidance on principal versus agent considerations. The guidance includes indicators to assist an entity in determining whether it controls a specified good or service before it is transferred to the customers. The amendments are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The Company is currently evaluating the impact that the adoption of this guidance will have on its consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASU 2016-02 requires the identification of arrangements that should be accounted for as leases by lessees. In general, for lease arrangements exceeding a twelve month term, these arrangements must now be recognized as assets and liabilities on the balance sheet of the lessee. Under ASU 2016-02, a right-of-use asset and lease obligation will be recorded for all leases, whether operating or financing, while the income statement will reflect lease expense for operating leases and amortization/interest expense for financing leases. The balance sheet amount recorded for existing leases at the date of adoption of ASU 2016-02 must be calculated using the applicable incremental borrowing rate at the date of adoption. In addition, ASU 2016-02 requires the use of the modified retrospective method, which will require adjustment to all comparative periods presented in the consolidated financial statements. The new guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company is currently evaluating the impact that the adoption of this guidance will have on its consolidated financial statements and the implementation approach to be used.

In June 2016, FASB issued ASU 2016-13, Financial Instruments - Credit Losses, which require a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. The allowance for credit losses is a valuation account that is to be deducted from the amortized cost basis of the financial asset(s) to present the net carrying value at the amount expected to be collected on the financial asset. The new guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The amendment should be applied through a modified retrospective approach. Early adoption as of the fiscal years beginning after December 15, 2018 is permitted. The adoption of ASU 2016-13 is not expected to have a material effect on its consolidated financial statements.

In August 2016, FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments. The amendments apply to all entities that are required to present a Statement of Cash Flows under Topic 230. The amendments are an improvement to GAAP because they provide guidance for each of the eight issues, thereby reducing the current and potential future diversity in practice. The amendments are effective for fiscal years beginning after December 15, 2017 and interim periods within those annual periods and should be applied using a retrospective transition method to each period presented. The Company does not expect the adoption of this ASU to have a material effect on its financial position or results of operations.

In November 2016, FASB issued ASU 2016-18, Statement of Cash Flows - Restricted cash. The amendments apply to all entities that have restricted cash or restricted cash equivalents and are required to present a Statement of Cash Flows under Topic 230. The amendments in this update require that a Statement of Cash Flows should explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. The amendments are effective for fiscal years beginning after December 15, 2017 and interim periods within those annual periods. Early adoption is permitted with an adjustment reflected as of the beginning of the fiscal year in which the amendment is adoption. The Company does not expect the adoption of this ASU to have a material effect on its financial position or results of operations.

In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (Topic 350), which eliminates Step 2 from the goodwill impairment test. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 is effective for annual and interim periods in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed after January 1, 2017 and should be applied prospectively. The Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements.

In March, 2017, FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost. The ASU amends ASC 715, Compensation — Retirement Benefits, to require employers that present a measure of operating income in their statement of income to include only the service cost component of net periodic pension cost and net periodic post-retirement benefit cost in operating expenses (together with other employee compensation costs). The other components of net benefit cost, including amortization of prior service cost/credit, and settlement and curtailment effects, are to be included in non-operating expenses. The update also stipulates that only the service cost component of net benefit cost is eligible for capitalization. The amendments are effective for fiscal years beginning after December 15, 2017 and interim periods within those annual periods. Early adoption is permitted as of the beginning of an annual period. The Company is currently evaluating the impact that the adoption of this guidance will have on its consolidated financial statements.