Income Taxes - Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Deferred Tax Liabilities, Gross [Abstract]
Depreciation and intangible amortization	$ (50,181)	$ (53,474)
Right-of-use assets	(12,683)	(6,522)
Other liabilities	(1,883)	(464)
Deferred tax liabilities	$ (64,747)	$ (60,460)