Selected Quarterly Financial Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Quarterly Financial Data [Line Items]
Net revenues	$ 235,324		$ 228,332		$ 228,250		$ 219,523		$ 223,287		$ 209,871		$ 202,501		$ 189,106		$ 911,429	[1]	$ 824,765	[1]	$ 723,903	[1]
Cost of revenues	137,856		133,804		138,702		123,500		118,169		112,158		118,920		111,329		533,862		460,576		408,919
Gross Profit	97,468		94,528		89,548		96,023		105,118		97,713		83,581		77,777		377,567		364,189		314,984
Selling, general and administrative expenses	24,109		26,566		26,321		32,221		29,759		22,445		18,690		25,693		109,217		96,587		103,044
Income from operations	73,359		67,962		63,227		63,802		75,359		75,268		64,891		52,084		268,350		267,602		211,940
Other income (expense), net	15,906		10,657		12,175		11,785		9,802	[2]	949	[2]	(1,335)	[2]	8,804	[2]	50,523		18,220	[2]	27,988
Income before income taxes	89,265		78,619		75,402		75,587		85,161		76,217		63,556		60,888		318,873		285,822		239,928
Income tax expense	18,563	[3]	17,013	[3]	16,118	[3]	17,439	[3]	18,856	[4]	16,800	[4]	16,044	[4]	14,464	[4]	69,133	[3]	66,164	[4]	54,385
Net income	$ 70,702		$ 61,606		$ 59,284		$ 58,148		$ 66,305		$ 59,417		$ 47,512		$ 46,424		$ 249,740		$ 219,658		$ 185,543
Earnings per share, diluted	$ 0.84	[5]	$ 0.73	[5]	$ 0.71	[5]	$ 0.69	[5]	$ 0.79	[5]	$ 0.71	[5]	$ 0.57	[5]	$ 0.55	[5]	$ 2.97	[5]	$ 2.62	[5]	$ 2.22
Weighted average shares outstanding, diluted	84,055		83,968		83,916		83,944		83,900		83,776		83,700		83,678		83,971		83,764		83,586

[1] Net revenues are attributed to regions based upon customer location.

[2] Other income, net includes interest expenses of $0.2 million, $0.4 million and $0.6 million regrouped from selling general and administration expenses for the quarters ended March 31, 2013, June 30, 2013 and September 30, 2013, respectively. For the quarter ended December 31, 2013, interest expenses of $0.6 million were reported under other income.

[3] The tax rate for the year ended December 31, 2014 was impacted by a favorable adjustment of $1.20 million, which related to the true up of tax provisions, pursuant to finalization of the tax computation of Syntel Limited, which had arisen on account of setoff of inter units unabsorbed expenses. Further, a $0.86 million tax charge has arisen on account of the particular tax dispute raised during the year. The Company has provided tax charges of $1.63 million and $0.88 million on account of valuation allowances against deferred tax assets recognized on investments and the minimum alternative tax, respectively. Without the above, the effective tax rate for the year ended December 31, 2014 would have been 21.1%.

[4] The tax rate for the year ended December 31, 2013 was impacted by a favorable adjustment of $1.09 million which related to the true up of tax provisions, pursuant to finalization of the tax computation for filing tax returns of Syntel Limited, which had arisen on account of finalization of the actual numbers of expenses apportionment, wage reconciliations, meal disallowances etc., compared with the amounts estimated earlier for the tax provisions. Further, a $0.43 million reversal of tax reserve has arisen on account of the reversal of a valuation allowance, created in the past, and against deferred tax assets recognized on the allowance on the accumulated losses. During the year ended December 31, 2013, the Company reviewed the filing requirements for certain U.S. State and City income tax returns. The Company has updated the profit apportionment method in those certain states and cities. Accordingly, the Company had provided $1.59 million, out of which $0.6 million relates to the prior years. Without the above, the effective tax rate for the year ended December 31, 2013 would have been 23.5%.

[5] Earnings per share for the quarter are computed independently and may not equal the earnings per share computed for the total year.