Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Current
State	$ 465	$ 359	$ 413
Total current income tax provision (benefit)	465	359	413
Deferred
Federal	(17,308)	17,713	8,982
State	(583)	2,802	531
Total deferred income tax provision (benefit)	(17,891)	20,515	9,513
(Benefit) provision for income taxes	$ (17,426)	$ 20,874	$ 9,926

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