Income Taxes - Unrecognized Tax Benefits - Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Tax Uncertainties [Abstract]
Unrecognized tax benefits	$ 1,679	$ 2,006	$ 16,722	$ 16,860
Unrecognized tax benefits, tax benefits that if recognized would impact the effective tax rate	1,679
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense [Abstract]
Interest related to unrecognized benefits	$ 0	$ 1,100	$ 1,100