Income Taxes - Summary of Components of Tax Provision (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Current
Federal	$ 418	$ 780	$ 6,313	$ 1,549
State	58	185	1,240	363
Deferred
Federal	2,919	4,785	(972)	5,666
State	626	1,268	(1,920)	1,412
Net benefit for income taxes	$ 4,021	$ 7,018	$ 4,661	$ 8,990

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