Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 61,733	$ 51,565	$ 32,445
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	34,580	31,465	28,028
Stock-based compensation expense	19,770	16,047	11,011
Unrealized foreign exchange gain	(1,001)	(3,798)	(424)
Deferred income taxes	(3,384)	2,238	76
Excess tax benefit from stock-based compensation	(4,326)	(1,458)	(1,181)
Change in fair value of earn-out consideration	(4,060)	0	0
Others, net	(107)	(278)	295
Change in operating assets and liabilities (net of effect of acquisitions):
Restricted cash	(2,137)	(787)	(747)
Accounts receivable	(18,062)	(9,087)	3,261
Prepaid expenses and other current assets	(5,421)	(3,112)	(3,930)
Accounts payable	(2,628)	44	(146)
Deferred revenue	5,726	2,566	(947)
Accrued employee costs	5,304	8,528	179
Accrued expenses and other liabilities	9,080	(4,699)	8,426
Advance income tax, net	437	8,865	(7,841)
Other assets	4,754	(1,408)	(1,846)
Net cash provided by operating activities	100,258	96,691	66,659
Cash flows from investing activities:
Purchase of property, plant and equipment	(25,850)	(25,585)	(27,678)
Business acquisition (net of cash acquired)	(28,666)	(44,270)	(58,185)
Purchase of short-term investments	(182,471)	(129,050)	(9,134)
Proceeds from redemption of short-term investments	182,320	125,365	6,735
Net cash used for investing activities	(54,667)	(73,540)	(88,262)
Cash flows from financing activities:
Principal payments on capital lease obligations	(348)	(720)	(967)
Proceeds from borrowings	0	30,000	50,000
Repayments of borrowings	(25,000)	(10,000)	0
Proceeds from non-controlling interest	0	176	0
Payment of debt issuance costs	0	(74)	(405)
Acquisition of treasury stock	(18,203)	(14,195)	(3,322)
Proceeds from exercise of stock options	6,499	3,375	6,459
Excess tax benefit from stock-based compensation	4,326	1,458	1,181
Net cash (used for)/provided by financing activities	(32,726)	10,020	52,946
Effect of exchange rate changes on cash and cash equivalents	(5,033)	(4,347)	(2,909)
Net increase in cash and cash equivalents	7,832	28,824	28,434
Cash and cash equivalents, beginning of year	205,323	176,499	148,065
Cash and cash equivalents, end of year	213,155	205,323	176,499
Supplemental disclosure of cash flow information:
Cash paid for interest	1,178	1,188	355
Cash paid for taxes, net of refund	15,667	11,505	11,204
Assets acquired under capital lease	$ 334	$ 215	$ 366