Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 37,166	$ 30,195
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,063	16,403
Stock-based compensation expense	11,063	10,259
Unrealized gain on short term investments	(2,246)	(2,984)
Change in fair value of earn-out consideration	0	(4,060)
Unrealized foreign exchange loss/(gain)	1,643	(42)
Deferred income tax (benefit)/expense	(3,118)	3,607
Others, net	27	(67)
Change in operating assets and liabilities:
Restricted cash	1,828	314
Accounts receivable	(9,775)	(19,621)
Prepaid expenses and other current assets	7,161	(1,177)
Accounts payable	5,295	(1,427)
Deferred revenue	(2,367)	4,996
Accrued employee costs	(11,612)	(10,282)
Accrued expenses and other liabilities	(6,074)	4,413
Advance income tax, net	(1,117)	(3,179)
Other assets	(36)	(433)
Net cash provided by operating activities	46,901	26,915
Cash flows from investing activities:
Purchase of property, plant and equipment	(20,447)	(14,872)
Purchase of investments	(169,422)	(132,275)
Proceeds from redemption of investments	39,475	41,179
Net cash used for investing activities	(150,394)	(105,968)
Cash flows from financing activities:
Principal payments on capital lease obligations	(94)	(240)
Repayments of borrowings	0	(25,000)
Acquisition of treasury stock	(23,332)	(9,704)
Proceeds from exercise of stock options	1,778	4,195
Net cash used for financing activities	(21,648)	(30,749)
Effect of exchange rate changes on cash and cash equivalents	1,400	(2,408)
Net decrease in cash and cash equivalents	(123,741)	(112,210)
Cash and cash equivalents, beginning of period	213,155	205,323
Cash and cash equivalents, end of period	$ 89,414	$ 93,113