CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 72,760	$ 99,266	$ 84,456
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	28,562	23,387	17,395
Bad debt expense	51	1,539	1,407
Deferred taxes	12,561	(3,304)	(15,328)
Stock-based compensation expense	52,407	49,244	45,833
Impairment charges and acquisition related adjustments	0	0	(1,183)
Excess tax benefit on stock-based compensation plans	0	(5,264)	(8,363)
Other	(4,010)	6,228	3,883
(Increase)/decrease in operating assets:
Accounts receivable	(58,745)	(30,612)	(47,694)
Unbilled revenues	(22,743)	34,777	(38,076)
Prepaid expenses and other assets	3,605	(4,791)	(574)
Increase/(decrease) in operating liabilities:
Accounts payable	1,221	741	(2,781)
Accrued expenses and other liabilities	37,282	(13,926)	25,694
Due to employees	1,933	5,261	2,752
Taxes payable	70,480	2,271	8,972
Net cash provided by operating activities	195,364	164,817	76,393
Cash flows used in investing activities:
Purchases of property and equipment	(29,806)	(29,317)	(13,272)
Payment for construction of corporate facilities	0	0	(4,692)
Employee housing loans issued	(648)	(2,006)	(2,054)
Proceeds from repayments of employee housing loans	2,565	2,177	2,249
Restricted cash and time deposits, net	8	29,595	(29,944)
Acquisition of businesses, net of cash acquired (Note 3)	(6,840)	(5,500)	(76,908)
Other investing activities, net	(1,452)	(4,271)	(873)
Net cash used in investing activities	(36,173)	(9,322)	(125,494)
Cash flows from financing activities:
Proceeds related to stock option exercises	53,984	17,996	20,675
Excess tax benefit on stock-based compensation plans	0	5,264	8,363
Payments of withholding taxes related to net share settlements of restricted stock units	(3,194)	(539)	0
Proceeds from debt (Note 12)	25,000	20,000	35,000
Repayment of debt (Note 12)	(25,103)	(30,129)	0
Acquisition of businesses, deferred consideration (Note 3)	0	(2,260)	(30,274)
Other financing activities, net	(941)	135	0
Net cash provided by financing activities	49,746	10,467	33,764
Effect of exchange rate changes on cash and cash equivalents	11,623	(3,386)	(5,748)
Net increase/(decrease) in cash and cash equivalents	220,560	162,576	(21,085)
Cash and cash equivalents, beginning of period	362,025	199,449	220,534
Cash and cash equivalents, end of period	582,585	362,025	199,449
Supplemental disclosures of cash flow information:
Income taxes	26,669	37,488	25,071
Bank interest	548	566	124
Supplemental disclosure of non-cash operating activities
Prepaid and other current assets write-off related to vendor advance	0	0	741
Supplemental disclosure of non-cash investing and financing activities
Deferred consideration payable	$ 0	$ 0	$ 603