Goodwill and Intangible Assets - Summary of Company's Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning Balance	$ 186,770	$ 171,535
Acquisitions	0	16,108
Currency translation adjustments	1,384	(873)
Ending Balance	188,154	186,770
Insurance
Goodwill [Roll Forward]
Beginning Balance	38,110	35,824
Acquisitions	0	2,510
Currency translation adjustments	130	(224)
Ending Balance	38,240	38,110
Healthcare
Goodwill [Roll Forward]
Beginning Balance	19,276	19,276
Acquisitions	0	0
Currency translation adjustments	0	0
Ending Balance	19,276	19,276
Travel, Transportation and Logistics
Goodwill [Roll Forward]
Beginning Balance	12,983	13,278
Acquisitions	0	0
Currency translation adjustments	570	(295)
Ending Balance	13,553	12,983
Finance and Accounting
Goodwill [Roll Forward]
Beginning Balance	47,537	47,891
Acquisitions	0	0
Currency translation adjustments	684	(354)
Ending Balance	48,221	47,537
All Other
Goodwill [Roll Forward]
Beginning Balance	5,326	5,326
Acquisitions	0	0
Currency translation adjustments	0	0
Ending Balance	5,326	5,326
Analytics
Goodwill [Roll Forward]
Beginning Balance	63,538	49,940
Acquisitions	0	13,598
Currency translation adjustments	0	0
Ending Balance	$ 63,538	$ 63,538

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

+ Details

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

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

+ Details

Name:	us-gaap_GoodwillForeignCurrencyTranslationGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=exls_InsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=exls_HealthcareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=exls_TravelTransportationandLogisticsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=exls_FinanceandAccountingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=exls_OtherOperationsManagementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=exls_AnalyticsAndBusinessTransformationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: