CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ 100,739	$ (39,873)	$ 44,102
Other comprehensive income (loss):
Unrealized gains (losses) on available-for-sale securities (net of taxes of $152, ($214) and $0, respectively)	32	(321)	0
Reclassification adjustment for losses on available-for-sale securities included in net income (net of taxes of $79, $0, $0, respectively)	143	0	0
Foreign currency translation adjustments (including a tax benefit of $16.8 million in 2016)	41,636	40,728	(144,050)
Unfunded pension liability (net of taxes of $38, $57 and $7, respectively)	108	159	0
Other comprehensive income (loss)	41,919	40,566	(144,050)
Comprehensive income (loss)	$ 142,658	$ 693	$ (99,948)