Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Reconciliation of Unrecognized Tax Benefits
Beginning balance	$ 3,568	$ 4,763	$ 3,085
Increase for tax positions taken during a prior period	396	547	2,135
Decrease for settlement for tax positions taken during a prior period	(259)	0	0
Decrease for tax positions as a result of the lapse of the statute of limitations	(412)	(1,742)	(457)
Ending balance	$ 3,293	$ 3,568	$ 4,763