Condensed 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	$ (117,333)	$ 125,664	$ (368,445)
Other comprehensive income (loss):
Cumulative translation gain (loss)	6	(4)	(6)
Comprehensive (loss) income	$ (117,327)	$ 125,660	$ (368,451)