Stock-Based Compensation - Restricted Stock Activity Under Company's Stock Plans (Parenthetical) (Detail) (Restricted Stock Units [Member])	Sep. 30, 2014	Dec. 31, 2013
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units vested for which underlying common stock to be issued	120,000	112,000

Restricted Stock Units Vested For Which Underlying Common Stock To Be Issued

No definition available.

Name:	exls_RestrictedStockUnitsVestedForWhichUnderlyingCommonStockToBeIssued
Namespace Prefix:	exls_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant