CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 289,775	$ 264,724	$ 274,922
Other comprehensive income (loss), net of tax
Reclassifications of losses to net income on derivatives designated as hedging instruments, net of tax of $(317), $(317) and $(317), respectively	1,054	1,053	1,054
Adjustment to postemployment benefit obligation, net of tax of $(706), $1,873 and $(8,657), respectively	2,384	(6,186)	28,648
Other comprehensive income (loss), net of tax	3,438	(5,133)	29,702
Comprehensive income	$ 293,213	$ 259,591	$ 304,624