Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 153,920	$ 38,251	$ 40,470
Other comprehensive income (loss):
Foreign currency translation adjustment	(174)	24	55
Tax benefit (provision)	61	(12)	(20)
Comprehensive income	$ 153,807	$ 38,263	$ 40,505