CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income	$ 114,758	$ 89,476	$ 67,659
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	49,656	50,513	52,193
Stock-based compensation expense	38,621	28,235	26,070
Amortization of operating lease right-of-use assets	26,326	27,146	27,335
Unrealized loss/(gain) on short term investments	5,139	(7,174)	(10,116)
Unrealized foreign currency exchange (gain)/loss, net	(3,821)	402	(206)
Deferred income tax (benefit)/expense	(20,327)	2,697	(12,345)
Reversal/(allowance) for expected credit losses	(464)	297	614
Loss on settlement of convertible notes	12,845	0	0
(Gain)/loss from equity-method investment	(47)	227	269
Amortization of non-cash interest expense related to convertible senior notes	1,795	2,616	2,472
Impairment charges	0	0	3,627
Others, net	216	(542)	(1,204)
Change in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(37,684)	24,696	(7,093)
Prepaid expenses and other current assets	(1,179)	(5,133)	1,385
Advance income tax, net	(12,062)	696	7,194
Other assets	227	6,505	(2,204)
Accounts payable	(614)	243	134
Deferred revenue	(12,733)	18,222	6,679
Accrued employee costs	46,475	335	16,915
Accrued expenses and other liabilities	2,934	(9,895)	13,856
Operating lease liabilities	(25,674)	(26,589)	(24,813)
Net cash provided by operating activities	184,387	202,973	168,421
Cash flows from investing activities:
Purchase of property and equipment	(37,248)	(42,224)	(40,545)
Proceeds from sale of property and equipment	1,300	916	407
Business acquisition (net of cash and cash equivalents acquired)	(76,831)	0	0
Purchases of investments	(96,011)	(102,462)	(187,974)
Proceeds from redemptions of investments	94,520	126,154	176,968
Investment in equity affiliate	0	(700)	0
Purchase of non-controlling interest	0	0	(241)
Net cash used for investing activities	(114,270)	(18,316)	(51,385)
Cash flows from financing activities:
Principal payments of finance lease liabilities	(201)	(249)	(336)
Proceeds from borrowings	300,000	110,000	46,000
Repayments of borrowings	(329,031)	(120,867)	(98,247)
Payment of debt issuance costs	0	0	(117)
Acquisition of treasury stock	(118,357)	(79,949)	(41,364)
Proceeds from exercise of stock options	710	1,501	986
Net cash used for financing activities	(146,879)	(89,564)	(93,078)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(4,947)	3,382	(1,045)
Net (decrease)/increase in cash, cash equivalents and restricted cash	(81,709)	98,475	22,913
Cash, cash equivalents and restricted cash at the beginning of the year	225,519	127,044	104,131
Cash, cash equivalents and restricted cash at the end of the year	143,810	225,519	127,044
Cash paid during the year for:
Interest	6,589	7,626	10,649
Income taxes, net of refunds	49,825	20,571	19,087
Supplemental disclosure of non-cash investing and financing activities:
Settlement of portion of convertible notes through issuance of treasury stock	36,742	0	0
Assets acquired under finance lease	$ 71	$ 45	$ 506