CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (154,175)	$ 3,030	$ (2,056)
Other comprehensive income (loss):
Foreign currency translation adjustments	3,352	(1,528)	(2,381)
Change in unrealized gain (loss) on available for sale securities	56,359	(56,359)	(228)
Change in fair value of derivatives qualifying as cash flow hedges	114	597	424
Other comprehensive income (loss) before income tax benefit (expense)	59,825	(57,290)	(2,185)
Income tax benefit (expense) related to items in other comprehensive loss	19	(297)	(78)
Total other comprehensive income (loss)	59,844	(57,587)	(2,263)
Comprehensive loss	(94,331)	(54,557)	(4,319)
Less: Comprehensive loss (income) attributable to non-controlling interests	1,566	(146)	(170)
Comprehensive loss, net	$ (92,765)	$ (54,703)	$ (4,489)