Income Taxes - Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Deferred Tax Liabilities, Gross [Abstract]
Depreciation and intangible amortization	$ (54,360)	$ (57,634)
Right-of-use assets	(9,524)
Deferred tax liabilities	$ (63,884)	$ (57,634)