Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 74,407	$ 73,016
Gross Unrealized Gain	65	12
Gross Unrealized (Loss)	(774)	(2,311)
Fair Value	73,698	70,717
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,606	4,335
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	0	0
Fair Value	2,606	4,335
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	59,615	50,471
Gross Unrealized Gain	65	0
Gross Unrealized (Loss)	(406)	(1,620)
Fair Value	59,274	48,851
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	12,186	18,210
Gross Unrealized Gain	0	12
Gross Unrealized (Loss)	(368)	(691)
Fair Value	$ 11,818	$ 17,531