Segment Information - Revenues and Cost of Revenues for Company's Operations Management and Analytics and Business Transformation Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues and cost of revenues for Company's outsourcing services and transformation services segments [Line Items]
Revenues, net	$ 171,200	$ 163,503	$ 508,714	$ 462,634
Cost of revenues (exclusive of depreciation and amortization)	111,767	103,198	332,172	296,801
Gross profit	59,433	60,305	176,542	165,833
Operating expenses	42,074	39,556	126,495	116,368
Foreign exchange gain and Other income, net	4,337	1,978	14,747	6,647
Income tax expense	5,646	7,565	18,549	19,309
Net income	16,050	15,162	46,245	36,803
Operations Management
Revenues and cost of revenues for Company's outsourcing services and transformation services segments [Line Items]
Revenues, net	129,563	128,043	388,502	376,943
Cost of revenues (exclusive of depreciation and amortization)	85,988	81,477	256,078	242,014
Gross profit	43,575	46,566	132,424	134,929
Analytics
Revenues and cost of revenues for Company's outsourcing services and transformation services segments [Line Items]
Revenues, net	41,637	35,460	120,212	85,691
Cost of revenues (exclusive of depreciation and amortization)	25,779	21,721	76,094	54,787
Gross profit	$ 15,858	$ 13,739	$ 44,118	$ 30,904