Income Taxes - Summary of components of provision (benefit) for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current provision (benefit):
Federal	$ 95,995	$ (43,993)	$ (24,727)
State	13,966	(24,479)	(3,638)
Foreign	2,953	4,567	7,898
Deferred provision (benefit):
Federal	(39,710)	(31,505)	(31,178)
State	(2,899)	(2,704)	(1,835)
Total income tax provision (benefit)	$ 70,305	$ (98,114)	$ (53,480)