Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Current federal	$ 0	$ (4,641)	$ (4,935)
Current state	1,126	485	693
Deferred federal	20,331	20,639	(31,291)
Deferred state	89	1,490	(1,684)
Total expense (benefit)	$ 21,546	$ 17,973	$ (37,217)