Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Detail) - Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets
Money market and mutual funds	$ 118,478	$ 127,347
Derivative financial instruments	4,184	4,579
Total	122,662	131,926
Liabilities
Derivative financial instruments	2,358	2,961
Fair value of earn-out consideration	4,060
Total	6,418	2,961
Level 1
Assets
Money market and mutual funds	118,478	127,347
Total	118,478	127,347
Level 2
Assets
Money market and mutual funds	0
Derivative financial instruments	4,184	4,579
Total	4,184	4,579
Liabilities
Derivative financial instruments	2,358	2,961
Total	2,358	2,961
Level 3
Assets
Money market and mutual funds	0
Liabilities
Derivative financial instruments	0	$ 0
Fair value of earn-out consideration	4,060
Total	$ 4,060

Fair Value Of Earn Out Consideration

No definition available.

Name:	exls_FairValueOfEarnOutConsideration
Namespace Prefix:	exls_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Money market and mutual fund fair value disclosure.

+ References

No definition available.

+ Details

Name:	exls_MoneyMarketAndMutualFundFairValueDisclosure
Namespace Prefix:	exls_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Fair value portion of asset contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward contracts, and swaps.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into.

+ References

No definition available.

+ Details

Name:	us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of financial and nonfinancial obligations.

+ References

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: