Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Current federal		$ 0	$ 0	$ (64)
Current state		859	595	520
Deferred federal		1,625	5,574	(314,651)
Deferred state		212	10,329	(10,374)
Total		2,696	16,498	(324,569)
Income Tax Contingency [Line Items]
Valuation allowances and reserves, adjustments			8,600	$ 335,200
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Valuation allowances and reserves, adjustments	$ 8,600	$ 3,500	$ 8,600