Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income tax computed at statutory rate			$ 12,112	$ 12,052	$ 7,596
State income taxes, net of federal benefit			111	1,287	4,974
Deferred rate change			110,071	0	(678)
(Decrease) increase in valuation allowance - other			(27,370)	(3,482)	6,457
Changes for uncertain tax positions			598	(685)	(40)
Stock based compensation			0	741	0
Permanent differences			2,133	496	400
Tax credits			(3,174)	(7,460)	(2,134)
Other, net			3	(253)	(77)
Total			$ 94,484	2,696	16,498
Income Tax Contingency [Line Items]
Federal tax rate for fiscal year provision, percent			24.50%
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Valuation allowances and reserves, adjustments	$ 27,400	$ 8,600		$ 3,500	$ 8,600