Income Taxes - Income Tax Expense (Benefit) from Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
U.S. federal	$ 123	$ 14,695	$ 7,470
State	962	2,048	514
Foreign	122	27	0
Total current expense	1,207	16,770	7,984
Deferred:
U.S. federal	(26,012)	(16,608)	(12,004)
State	(1,022)	(1,421)	(538)
Foreign	(63)	(26)	(65)
Total deferred benefit	(27,097)	(18,055)	(12,607)
Income tax benefit	$ (25,890)	$ (1,285)	$ (4,623)