CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities:
Net income	$ 19,200	$ 43,694
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,483	12,009
Bad debt expense	1,053	1,726
Deferred taxes	(6,667)	(5,508)
Share-based compensation expense	11,132	10,557
Changes in operating assets and liabilities:
Accounts receivable	9,300	18,804
Prepaid expenses and other current assets	(1,075)	(5,042)
Deposits and other assets	(956)	(1,288)
Accounts payable and accrued expenses	(5,816)	(14,468)
Accrued compensation and employee benefits	(3,901)	(10,437)
Deferred revenue and advance payments	(4,032)	1,140
Other long-term liabilities	1,527	(1,904)
Net cash provided by operating activities	23,248	49,283
Investing activities:
Proceeds from redemption of short-term investments	348,980	340,920
Purchases of property and equipment	(4,457)	(2,282)
Purchases of short-term investments	(674,528)	(411,666)
Net cash used in investing activities	(330,005)	(73,028)
Financing activities:
Proceeds from sale of class A common stock under exercise of employee stock options	2,471	1,677
Payments on capital lease obligations and other financing arrangements	(9)	(17)
Net cash provided by financing activities	2,462	1,660
Effect of foreign exchange rate changes on cash, cash equivalents, and restricted cash	(3,904)	6,992
Net decrease in cash, cash equivalents, and restricted cash	(308,199)	(15,093)
Cash, cash equivalents and restricted cash, beginning of period	421,182	402,712
Cash, cash equivalents and restricted cash, end of period	$ 112,983	$ 387,619