Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Components of Deferred Tax Assets and Liabilities [Abstract]
Deferred tax assets	$ 63,075	$ 56,736
Deferred tax liabilities	(63,884)	(57,634)
Valuation allowance	(13,599)	(16,093)
Net deferred tax (liability)	$ (14,408)	$ (16,991)