Segment and Geographical Information - Revenues and Cost of Revenues for Company's Reportable Segments (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net		$ 222,473	$ 243,509	$ 468,463	$ 483,082
Cost of revenues	[1]	158,401	162,446	321,057	319,686
Gross profit	[1]	64,072	81,063	147,406	163,396
Operating expenses		54,206	67,207	110,053	132,679
Foreign exchange gain, interest expense and other income, net		2,701	1,440	3,535	3,541
Income tax expense		4,072	2,670	9,927	6,870
Loss from equity-method investment		66	62	121	129
Net income attributable to ExlService Holdings, Inc. stockholders		8,429	12,564	30,840	27,259
BPM and related services
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net		140,794	155,638	294,353	308,250
Analytics services
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net		81,679	87,871	174,110	174,832
Insurance
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net		81,281	85,581	165,020	166,867
Cost of revenues		59,113	59,414	118,078	114,657
Gross profit		22,168	26,167	46,942	52,210
Healthcare
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net		24,978	21,730	52,007	43,978
Cost of revenues		19,640	17,749	39,233	35,551
Gross profit		5,338	3,981	12,774	8,427
Emerging Business
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net		34,535	48,327	77,326	97,405
Cost of revenues		22,416	27,852	47,898	55,145
Gross profit		12,119	20,475	29,428	42,260
Analytics
Revenues and cost of revenues for Company's reportable segments [Line Items]
Revenues, net		81,679	87,871	174,110	174,832
Cost of revenues		57,232	57,431	115,848	114,333
Gross profit		$ 24,447	$ 30,440	$ 58,262	$ 60,499

[1] Exclusive of depreciation and amortization expense.