Income Taxes - Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ (500)
State	600	$ 600	$ 600
Foreign	800
Gross	900	600	600
Deferred
Federal	70,100	12,000	12,800
State	12,500	500	3,000
Foreign	(700)
Gross	81,900	12,500	15,800
Total provision (benefit) for taxes	$ 82,809	$ 13,121	$ 16,414