Income Taxes - Summary of Income Tax Benefit (Expense) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Current income tax benefit (expense):
Federal									$ (1,841)	$ (16,449)	$ (10,078)
State									(372)	(2,858)	(813)
Deferred income tax benefit (expense):
Federal									2,431	(2,245)	1,503
State									608	387	151
Total tax (expense) benefit	$ 486	$ 866	$ 3,204	$ (3,730)	$ (8,461)	$ (3,690)	$ (5,370)	$ (3,644)	$ 826	$ (21,165)	$ (9,237)