Stock Based Compensation - Performance Based Stock Awards Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
Jun. 15, 2018	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Amendment And Restatement Of The 2006 Omnibus Award Plan (2015 Plan)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance based percentage		100.00%
Revenue Based PRSUs \| Amendment And Restatement Of The 2006 Omnibus Award Plan (2015 Plan)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance based percentage		50.00%
Vesting period		3 years
Market Condition Based PRSUs \| Amendment And Restatement Of The 2006 Omnibus Award Plan (2015 Plan)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance based percentage		50.00%
Vesting period		3 years
Market Condition Based PRSUs \| Amendment And Restatement Of The 2006 Omnibus Award Plan (2015 Plan) \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target shares an employee can earn		200.00%
Performance Based Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost		$ 12,964
Cost not yet recognized, period for recognition		1 year 8 months 12 days

Percentage Of Performance Criteria Achieved And Shares Vested

No definition available.

Name:	exls_PercentageOfPerformanceCriteriaAchievedAndSharesVested
Namespace Prefix:	exls_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Share Based Compensation Arrangement By Share Based Payment Award Percentage Of Target Shares Earned

+ References

No definition available.

+ Details

Name:	exls_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfTargetSharesEarned
Namespace Prefix:	exls_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PlanNameAxis=exls_AmendmentAndRestatementOfThe2006OmnibusAwardPlan2015PlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=exls_RevenueBasedPerformanceRestrictedStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=exls_MarketConditionBasedPerformanceRestrictedStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=exls_PerformanceBasedStockAwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: