CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 149,809	$ 73,846	$ 230,854	$ 149,598
Other comprehensive income, net of tax
Reclassifications of losses to net income on derivatives designated as hedging instruments, net of tax of $(79), $0, $(191) and $0, respectively	263	0	494	0
Loss on derivatives designated as hedging instruments, net of tax of $0, $2,781, $0 and $2,781, respectively	0	(9,711)	0	(9,711)
Adjustment to postemployment benefit obligation, net of tax of $(244), $(1,753), $(489) and $(1,970), respectively	813	6,100	1,625	6,859
Other comprehensive income (loss)	1,076	(3,611)	2,119	(2,852)
Comprehensive income	$ 150,885	$ 70,235	$ 232,973	$ 146,746