CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 14,489	$ 37,860
Other comprehensive income:
Unrealized gain on pension plan obligation	224	235
Tax effect of unrealized gain on pension plan obligation	(45)	(64)
Unrealized loss on captive insurance collateral	(612)	(340)
Tax effect of unrealized loss on captive insurance collateral	129	72
Unrealized gain on interest rate hedges	718	332
Tax effect of unrealized gain on interest rate hedges	(193)	(88)
Total other comprehensive income	221	147
Total comprehensive income	$ 14,710	$ 38,007