Consolidated Statements of Income - USD ($)		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Income Statement [Abstract]
Revenues, net		$ 883,112,000		$ 762,310,000	[1]	$ 685,988,000	[1]
Cost of revenues		584,855,000	[1],[2]	495,142,000	[1],[2]	447,718,000
Gross profit	[2]	298,257,000		267,168,000	[1]	238,270,000	[1]
Operating expenses:
General & administrative expenses		116,202,000	[1]	102,515,000	[1]	88,616,000
Selling & marketing expenses		63,612,000	[1]	53,379,000	[1]	50,579,000
Depreciation and amortization		48,566,000		38,549,000	[1]	34,580,000
Impairment charges		20,056,000		0	[1],[3]	0	[1],[3]
Total operating expenses	[1]	248,436,000		194,443,000		173,775,000
Income from operations		49,821,000		72,725,000	[1]	64,495,000	[1]
Foreign exchange gain, net		4,787,000		2,839,000	[1]	5,597,000	[1]
Interest expense		(7,227,000)		(1,889,000)	[1]	(1,343,000)	[1]
Other income, net		12,989,000	[1]	11,359,000	[4]	15,135,000	[4]
Income before income tax expense		60,370,000		85,034,000	[1]	83,884,000	[1]
Income tax expense		3,397,000		36,146,000	[1]	22,151,000	[1]
Loss from equity-method investment		247,000		0	[1],[3]	0	[1],[3]
Net income attributable to ExlService Holdings, Inc. stockholders		$ 56,726,000		$ 48,888,000	[1],[3]	$ 61,733,000	[1],[3]
Earnings per share attributable to ExlService Holdings, Inc. stockholders:
Basic (in dollars per share)		$ 1.65		$ 1.44	[1]	$ 1.84	[1]
Diluted (in dollars per share)		$ 1.62		$ 1.39	[1]	$ 1.79	[1]
Weighted-average number of shares used in computing earnings per share:
Basic (in shares)		34,451,008		33,897,916	[1]	33,566,367	[1]
Diluted (in shares)		35,030,984		35,110,210	[1]	34,563,319	[1]

[1] Adjusted pursuant to adoption of ASU No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost. Refer to Note 21 and Note 27 to the consolidated financial statements.

[2] Exclusive of depreciation and amortization.

[3] Adjusted pursuant to adoption of ASU 2016-18, Statements of Cash Flows, Restricted Cash. Refer to Note 8 and Note 27 to the consolidated financial statements.

[4] These are reclassified to net income and are included in other income, net in the consolidated statements of income. Refer to Note 21 to the consolidated financial statements.