Income Taxes - Schedule of Unrecognized Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefit, beginning of year	$ 65,035	$ 50,742	$ 23,923
Tax positions related to current year:
Additions	14,736	7,570	7,075
Tax positions related to prior years:
Additions	104,375	10,705	20,855
Reductions	(9,669)	(452)	0
Settlements	(16,753)	(3,530)	0
Statute expirations	0	0	(1,111)
Unrecognized tax benefit, end of year	$ 157,724	$ 65,035	$ 50,742