Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 58,243	$ 46,245
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	28,771	25,000
Stock-based compensation expense	16,771	14,743
Unrealized gain on short term investments	(4,437)	(4,955)
Change in fair value of earn-out consideration	0	(4,060)
Unrealized foreign exchange loss/(gain)	446	(147)
Deferred income tax (benefit)/expense	(5,417)	4,424
Allowances for doubtful accounts	2,706	37
Others, net	12	(84)
Change in operating assets and liabilities:
Restricted cash	1,757	(464)
Accounts receivable	(22,064)	(16,559)
Prepaid expenses and other current assets	5,194	(587)
Accounts payable	371	(2,518)
Deferred revenue	(8,155)	(1,485)
Accrued employee costs	(915)	(3,812)
Accrued expenses and other liabilities	267	5,688
Advance income tax, net	(2,607)	(4,748)
Other assets	1,241	(676)
Net cash provided by operating activities	72,184	56,042
Cash flows from investing activities:
Purchase of property, plant and equipment	(26,759)	(20,335)
Business acquisition (net of cash acquired)	(724)	(9,427)
Purchase of investments	(197,897)	(155,709)
Proceeds from redemption of investments	54,238	59,229
Net cash used for investing activities	(171,142)	(126,242)
Cash flows from financing activities:
Principal payments on capital lease obligations	(133)	(292)
Repayments of borrowings	0	(25,000)
Acquisition of treasury stock	(32,336)	(15,169)
Proceeds from exercise of stock options	4,275	6,226
Net cash used for financing activities	(28,194)	(34,235)
Effect of exchange rate changes on cash and cash equivalents	1,662	(2,514)
Net decrease in cash and cash equivalents	(125,490)	(106,949)
Cash and cash equivalents, beginning of period	213,155	205,323
Cash and cash equivalents, end of period	$ 87,665	$ 98,374