CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (27,219)	$ (8,402)	$ 150,647	$ 151,419
Other comprehensive (loss) income, net of tax
Loss on derivatives designated as hedging instruments, net of tax of $180, $0, $2,961 and $0, respectively	(626)	0	(10,337)	0
Adjustment to postemployment benefit obligation, net of tax of $(191), $(118), $(2,161) and $(333), respectively	663	305	7,522	844
Other comprehensive income (loss)	37	305	(2,815)	844
Comprehensive (loss) income	$ (27,182)	$ (8,097)	$ 147,832	$ 152,263