CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 264,724	$ 274,922	$ 117,890
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 $(350), respectively	1,053	1,054	1,021
Adjustment to postemployment benefit obligation, net of tax of $1,873, $(8,657) and $(2,575), respectively	(6,186)	28,648	8,766
Other comprehensive (loss) income, net of tax	(5,133)	29,702	9,787
Comprehensive income	$ 259,591	$ 304,624	$ 127,677