Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues, net		$ 231,124	$ 192,345	$ 648,209	$ 564,435
Cost of revenues	[1]	152,157	123,077	429,907	365,883
Gross profit	[1]	78,967	69,268	218,302	198,552
Operating expenses:
General and administrative expenses		28,704	26,545	85,610	75,007
Selling and marketing expenses		16,490	12,196	45,593	38,631
Depreciation and amortization		14,099	9,582	35,185	28,489
Total operating expenses		59,293	48,323	166,388	142,127
Income from operations		19,674	20,945	51,914	56,425
Foreign exchange gain, net		1,385	637	3,414	1,905
Interest expense		(2,475)	(482)	(3,719)	(1,380)
Other income, net		2,466	2,796	8,232	8,495
Income before income tax expense		21,050	23,896	59,841	65,445
Income tax expense		5,739	2,819	6,796	7,202
Loss from equity-method investment		62	0	176	0
Net income attributable to ExlService Holdings, Inc. stockholders		$ 15,249	$ 21,077	$ 52,869	$ 58,243
Earnings per share attributable to ExlService Holdings, Inc. stockholders:
Basic (in dollars per share)		$ 0.44	$ 0.62	$ 1.53	$ 1.72
Diluted (in dollars per share)		$ 0.43	$ 0.60	$ 1.50	$ 1.66
Weighted-average number of shares used in computing earnings per share attributable to ExlService Holdings, Inc. stockholders:
Basic (in shares)		34,458,520	33,838,374	34,472,232	33,834,392
Diluted (in shares)		35,207,991	35,043,987	35,217,814	35,048,672

[1] Exclusive of depreciation and amortization.