Segment and Geographical Information - Revenues and Cost of Revenues for Company's Reportable Segments (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) operating_segment	Sep. 30, 2016 USD ($)
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	$ 192,345	$ 171,200	$ 564,435	$ 508,714
Cost of revenues (exclusive of depreciation and amortization)	124,890	111,767	370,458	332,172
Gross profit	67,455	59,433	193,977	176,542
Operating expenses	48,800	42,074	143,291	126,495
Foreign exchange gain, interest expense and other income, net	5,241	4,337	14,759	14,747
Income tax expense	2,819	5,646	7,202	18,549
Net income	21,077	16,050	$ 58,243	46,245
Number of operating segments, industry focused | operating_segment			5
Number of capability operating segments | operating_segment			1
BPM and related services
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	138,601	129,563	$ 410,125	388,502
Analytics services
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	53,744	41,637	154,310	120,212
Insurance
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	59,608	52,801	173,784	151,696
Cost of revenues (exclusive of depreciation and amortization)	39,699	37,797	119,004	108,516
Gross profit	19,909	15,004	54,780	43,180
Healthcare
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	18,871	15,959	56,726	49,788
Cost of revenues (exclusive of depreciation and amortization)	11,966	10,887	36,402	32,440
Gross profit	6,905	5,072	20,324	17,348
TT&L
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	18,496	17,519	53,374	52,623
Cost of revenues (exclusive of depreciation and amortization)	10,135	10,637	30,832	31,901
Gross profit	8,361	6,882	22,542	20,722
F&A
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	21,642	19,858	63,694	58,961
Cost of revenues (exclusive of depreciation and amortization)	13,310	12,012	39,163	35,385
Gross profit	8,332	7,846	24,531	23,576
All Other
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	19,984	23,426	62,547	75,434
Cost of revenues (exclusive of depreciation and amortization)	13,629	14,655	42,770	47,836
Gross profit	6,355	8,771	19,777	27,598
Analytics
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net	53,744	41,637	154,310	120,212
Cost of revenues (exclusive of depreciation and amortization)	36,151	25,779	102,287	76,094
Gross profit	$ 17,593	$ 15,858	$ 52,023	$ 44,118