Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 71,242	$ 70,633
Gross Unrealized Gain	6	0
Gross Unrealized (Loss)	(2,897)	(3,971)
Fair Value	68,351	66,662
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	537	1,838
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	0	0
Fair Value	537	1,838
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	50,471	48,473
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(2,156)	(3,052)
Fair Value	48,315	45,421
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	20,234	20,322
Gross Unrealized Gain	6	0
Gross Unrealized (Loss)	(741)	(919)
Fair Value	$ 19,499	$ 19,403