Income Taxes - Components of Income Tax Benefit from Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 0	$ (125)
State	17	50
Total current income tax benefit (expense)	17	(75)
Deferred:
Federal	1,958	0
State	(60)	0
Total deferred income tax benefit (expense)	1,898	0
Total income tax benefit (expense)	$ 1,915	$ (75)