Income Taxes - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Contingency [Line Items]
Federal net operating loss carryforwards			$ 133,200,000
State net operating loss carryforwards			39,600,000
Alternative minimum tax credit			9,600,000
General business credits			17,700,000
Income tax expense (benefit) from continuing operations			94,484,000	$ 2,696,000	$ 16,498,000
Pre-tax income required to realize deferred tax assets prior to expiration			768,000,000
Deferred tax asset valuation allowance	$ 65,159,000		34,212,000	65,159,000
Unrecognized tax benefits	3,804,000	$ 4,541,000	3,494,000	3,804,000	4,541,000	$ 4,721,000
Accrued interest and penalties	1,400		1,300	1,400
Uncertain tax positions to be reserved within twelve months			$ 21,600
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Valuation allowances and reserves, adjustments	$ 27,400,000	$ 8,600,000		$ 3,500,000	$ 8,600,000