Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Components of Deferred Tax Assets and Liabilities [Abstract]
Deferred tax assets	$ 56,736	$ 71,915
Deferred tax liabilities	(57,634)	(19,476)
Valuation allowance	(16,093)	(18,581)
Net deferred tax asset		$ 33,858
Net deferred tax (liability)	$ (16,991)