CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (10,587)	$ (12,054)	$ 85,281	$ 110,970
Other comprehensive income (loss):
Unrealized gain on pension plan obligation	224	234	672	704
Tax effect of unrealized gain on pension plan obligation	(61)	(65)	(167)	(193)
Unrealized loss on captive insurance collateral	(812)	(47)	(3,486)	(913)
Tax effect of unrealized loss on captive insurance collateral	171	11	735	193
Unrealized gain on interest rate hedges	623	252	2,890	1,303
Tax effect of unrealized gain on interest rate hedges	(165)	(66)	(768)	(344)
Total other comprehensive income (loss)	(20)	319	(124)	750
Total comprehensive income (loss)	$ (10,607)	$ (11,735)	$ 85,157	$ 111,720