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 income (loss)	$ (22,862)	$ 6,820	$ 211,388
Other comprehensive income (loss):
Foreign currency translation adjustment	7,798	(13,485)	9
Unrealized gain (loss) on marketable securities, net of tax	613	(396)	766
Total comprehensive income (loss)	$ (14,451)	$ (7,061)	$ 212,163