Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Tax Credit Carryforward [Line Items]
Federal net operating loss carryforwards	$ 26,500
Federal and state net operating loss and tax credit carryforwards	138,856	$ 149,299
State net operating loss carryforwards	37,600
Valuation allowance	(30,438)	(25,396)
Pre-tax income required to realize deferred tax assets prior to expiration	712,900
Unrecognized tax benefits	3,358	$ 3,358	$ 3,358	$ 3,441
Federal tax authority
Tax Credit Carryforward [Line Items]
Federal and state net operating loss and tax credit carryforwards	$ 78,100