UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net (loss) income	$ (61,013)	$ 1,791
Adjustments to reconcile net (loss) income to cash provided by operating activities
Stock-based compensation	38,397	31,165
Amortization and depreciation	33,788	20,921
Foreign currency transaction loss (gain)	1,607	(159)
Other non-cash	(230)	(846)
Change in operating assets and liabilities, net	(4,829)	22,560
Cash provided by operating activities	7,720	75,432
Investing activities
Purchases of investments	(10,497)	(51,395)
Proceeds from maturities and called investments	13,545	11,546
Sales of investments	29,965	0
Payments for acquisitions, net of cash acquired	(10,921)	0
Investment in property and equipment	(4,882)	(6,520)
Cash provided by (used in) investing activities	17,210	(46,369)
Financing activities
Dividend payments to shareholders	(4,730)	(4,702)
Common stock repurchases	(39,637)	(41,123)
Cash (used in) financing activities	(44,367)	(45,825)
Effect of exchange rate changes on cash and cash equivalents	515	(1,226)
Net (decrease) in cash and cash equivalents	(18,922)	(17,988)
Cash and cash equivalents, beginning of period	114,422	162,279
Cash and cash equivalents, end of period	$ 95,500	$ 144,291