Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits - beginning balance	$ 52,683	$ 32,792	$ 30,921
Decrease resulting from prior period tax positions	(631)	(721)
Increase resulting from prior period tax positions			671
Increase resulting from current period tax positions	6,586	20,612	1,200
Unrecognized tax benefits - ending balance	58,638	52,683	32,792
Less: deferred federal and state income tax benefits	(12,314)	(11,063)	(6,886)
Total unrecognized tax benefits that, if recognized, would impact the effective income tax rate as of the end of the year	$ 46,324	$ 41,620	$ 25,906