Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 75,301	$ 73,016
Gross Unrealized Gain	108	12
Gross Unrealized (Loss)	(558)	(2,311)
Fair Value	74,851	70,717
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	5,741	4,335
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	0	0
Fair Value	5,741	4,335
U.S. Government Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	57,095
Gross Unrealized Gain	108
Gross Unrealized (Loss)	(104)
Fair Value	57,099
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		50,471
Gross Unrealized Gain		0
Gross Unrealized (Loss)		(1,620)
Fair Value		48,851
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	12,465	18,210
Gross Unrealized Gain	0	12
Gross Unrealized (Loss)	(454)	(691)
Fair Value	$ 12,011	$ 17,531