CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 335,627	$ 289,775	$ 264,724
Other comprehensive (loss) income, net of tax
Reclassifications of losses to net income on derivatives designated as hedging instruments, net of tax of $(317), $(317) and $(317), respectively	1,052	1,054	1,053
Adjustment to postemployment benefit obligation, net of tax of $1,803, $(706) and $1,873, respectively	(5,994)	2,384	(6,186)
Other comprehensive (loss) income, net of tax	(4,942)	3,438	(5,133)
Comprehensive income	$ 330,685	$ 293,213	$ 259,591