Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 78,311	$ 75,301
Gross Unrealized Gain	79	108
Gross Unrealized (Loss)	(201)	(558)
Fair Value	78,189	74,851
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	343	5,741
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	0	0
Fair Value	343	5,741
U.S. Government Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	71,453
Gross Unrealized Gain	79
Gross Unrealized (Loss)	(11)
Fair Value	71,521
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		57,095
Gross Unrealized Gain		108
Gross Unrealized (Loss)		(104)
Fair Value		57,099
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	6,515	12,465
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(190)	(454)
Fair Value	$ 6,325	$ 12,011