Income Taxes - Effective Income Tax Rate Reconciliation (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]
Income tax computed at statutory rate		$ 12,052	$ 7,596	$ 7,711
State income taxes, net of federal benefit		1,287	4,974	2,485
Increase (decrease) in valuation allowance - other		(3,482)	6,457	(334,605)
Changes for uncertain tax positions		(685)	(40)	42
Stock based compensation		741	0	0
State rate change		0	(678)	0
Tax credits		(7,460)	(2,134)	0
Other, net		243	323	(202)
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

Effective Income Tax Rate Reconciliation, IRS Interest Refund

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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