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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues and cost of revenues for Company's outsourcing services and transformation services segments [Line Items]
Revenues, net	$ 170,478	$ 155,621	$ 337,514	$ 299,131
Cost of revenues (exclusive of depreciation and amortization)	112,026	100,478	220,405	193,603
Gross profit	58,452	55,143	117,109	105,528
Operating expenses	42,216	39,895	84,421	76,812
Foreign exchange gain and Other income, net	7,147	2,357	10,410	4,669
Income tax expense	7,008	5,531	12,903	11,744
Net income	16,375	12,074	30,195	21,641
Operating Segments | Operations Management
Revenues and cost of revenues for Company's outsourcing services and transformation services segments [Line Items]
Revenues, net	130,869	125,048	258,939	248,901
Cost of revenues (exclusive of depreciation and amortization)	86,482	80,809	170,090	160,538
Gross profit	44,387	44,239	88,849	88,363
Operating Segments | Analytics
Revenues and cost of revenues for Company's outsourcing services and transformation services segments [Line Items]
Revenues, net	39,609	30,573	78,575	50,230
Cost of revenues (exclusive of depreciation and amortization)	25,544	19,669	50,315	33,065
Gross profit	$ 14,065	$ 10,904	$ 28,260	$ 17,165