Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Current:
Federal	$ 123,340	$ 110,402	$ 112,456
State	23,818	10,199	16,844
Foreign	35,977	35,943	42,327
Current income tax	183,135	156,544	171,627
Deferred:
Federal	(26,949)	(26,227)	(37,884)
State	(3,330)	(1,712)	(15,025)
Foreign	(2,207)	609	5,531
Deferred income taxes	(32,486)	(27,330)	(47,378)
Total provision	$ 150,649	$ 129,214	$ 124,249