Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 51,565	$ 32,445	$ 48,097
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,465	28,028	24,917
Write-off of accounts receivable	0	0	2,029
Stock-based compensation expense	16,047	11,011	11,832
Unrealized foreign exchange gain	(3,798)	(424)	(7,782)
Deferred income taxes	2,238	76	2,484
Excess tax benefit from stock-based compensation	(1,458)	(1,181)	(1,953)
Others, net	(278)	295	343
Change in operating assets and liabilities (net of effect of acquisitions):
Restricted cash	(787)	(747)	(62)
Accounts receivable	(9,087)	3,261	(5,678)
Prepaid expenses and other current assets	(3,112)	(3,930)	(3,418)
Accounts payable	44	(146)	(375)
Deferred revenue	2,566	(947)	696
Accrued employee costs	8,528	179	3,306
Accrued expenses and other liabilities	(4,699)	8,426	5,565
Advance income tax, net	8,865	(7,841)	2,106
Other assets	(1,408)	(1,846)	685
Net cash provided by operating activities	96,691	66,659	82,792
Cash flows from investing activities:
Purchase of fixed assets	(25,585)	(27,678)	(15,916)
Business acquisition (net of cash acquired)	(44,270)	(58,185)	(1,183)
Purchase of short-term investments	(129,050)	(9,134)	(1,927)
Proceeds from redemption of short-term investments	125,365	6,735	1,491
Net cash used for investing activities	(73,540)	(88,262)	(17,535)
Cash flows from financing activities:
Principal payments on capital lease obligations	(720)	(967)	(1,511)
Proceeds from borrowings	30,000	50,000	0
Repayments of borrowings	(10,000)	0	0
Payment for purchase of non-controlling interest	0	0	(27)
Proceeds from non-controlling interest	176	0	0
Payment of debt issuance costs	(74)	(405)	0
Acquisition of treasury stock	(14,195)	(3,322)	(21,618)
Proceeds from exercise of stock options	3,375	6,459	5,489
Excess tax benefit from stock-based compensation	1,458	1,181	1,953
Net cash (used for)/provided by financing activities	10,020	52,946	(15,714)
Net cash (used for)/provided by financing activities	(4,347)	(2,909)	(4,515)
Net increase in cash and cash equivalents	28,824	28,434	45,028
Cash and cash equivalents, beginning of year	176,499	148,065	103,037
Cash and cash equivalents, end of year	205,323	176,499	148,065
Supplemental disclosure of cash flow information:
Cash paid for interest	1,188	355	592
Cash paid for taxes, net of refund	11,505	11,204	8,585
Assets acquired under capital lease	$ 215	$ 366	$ 288