UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 30,747	$ 25,880	$ 18,116	$ 4,487
Other comprehensive (loss) income:
Unrealized (losses) gains on available-for-sale securities (net of tax of $8, $20, $88 and $122, respectively)	(11)	27	(206)	159
Reclassification adjustment for losses on available-for-sale securities included in net income (net of taxes of $0, $29, $0 and $79, respectively)	0	47	0	143
Foreign currency translation adjustments (including a tax benefit of $5.6 million in 2018)	(4,931)	15,024	(21,482)	20,847
Other comprehensive (loss) income	(4,942)	15,098	(21,688)	21,149
Comprehensive income (loss)	$ 25,805	$ 40,978	$ (3,572)	$ 25,636