CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 117,890	$ 163,007	$ 123,935
Other comprehensive income (loss), net of tax:
Reclassifications of losses to net income on derivatives designated as hedging instruments, net of tax of $(350), $(32) and $0, respectively	1,021	108	0
Loss on derivatives designated as hedging instruments, net of tax of $0, $3,203 and $0, respectively	0	(10,505)	0
Adjustment to postemployment benefit obligation, net of tax of $(2,575), $567, and $6,106, respectively	8,766	(2,131)	(15,731)
Other comprehensive income (loss)	9,787	(12,528)	(15,731)
Comprehensive income	$ 127,677	$ 150,479	$ 108,204