Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 46,303	$ 52,869
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	39,633	35,345
Stock-based compensation expense	21,538	17,311
Amortization of operating lease right-of-use assets	20,544
Unrealized gain on short term investments	(7,443)	(5,423)
Unrealized foreign exchange loss/(gain), net	19	(14,375)
Deferred income tax benefit	(6,859)	(986)
Allowance for doubtful accounts receivable	433	(620)
Loss from equity-method investment	198	176
Amortization of non-cash interest expense related to convertible senior notes	1,836	0
Impairment charges	3,167	0
Others, net	(148)	193
Change in operating assets and liabilities:
Accounts receivable	(16,475)	(9,354)
Prepaid expenses and other current assets	752	(3,344)
Advance income tax, net	6,212	(4,228)
Other assets	(1,307)	(5,597)
Accounts payable	(1,847)	(1,414)
Deferred revenue	3,247	(5,199)
Accrued employee costs	3,420	(7,680)
Accrued expenses and other liabilities	12,160	(436)
Operating lease liabilities	(19,428)
Net cash provided by operating activities	105,955	47,238
Cash flows from investing activities:
Purchase of property and equipment	(32,308)	(30,070)
Purchase of non-controlling interest	(241)	0
Business acquisition (net of cash acquired)	0	(231,918)
Purchase of investments	(117,934)	(57,957)
Proceeds from redemption of investments	129,143	79,536
Net cash used for investing activities	(21,340)	(240,409)
Cash flows from financing activities:
Principal payments on finance lease liabilities	(274)	(105)
Proceeds from borrowings	46,000	245,000
Repayments of borrowings	(87,763)	(5,083)
Payment of debt issuance costs	(117)	(387)
Acquisition of treasury stock	(35,884)	(32,793)
Proceeds from exercise of stock options	338	1,084
Net cash (used for) / provided by financing activities	(77,700)	207,716
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1,761)	(3,008)
Net increase in cash, cash equivalents and restricted cash	5,154	11,537
Cash, cash equivalents and restricted cash at beginning of period	104,131	94,277
Cash, cash equivalents and restricted cash at end of period	109,285	105,814
Non-cash investing and financing transaction
Restricted common stock issued for business acquisition	$ 0	$ 4,080