Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Components of Deferred Tax Assets and Liabilities [Abstract]
Deferred tax assets	$ 68,090	$ 55,710
Deferred tax liabilities	(64,747)	(60,460)
Valuation allowance	(8,592)	(10,623)
Net deferred tax liability	$ (5,249)	$ (15,373)