Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 69,397	$ 68,951
Gross Unrealized Gain	13	1,053
Gross Unrealized (Loss)	(2,517)	(71)
Fair Value	66,893	69,933
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	574	515
Fair Value	574	515
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	48,473	51,632
Gross Unrealized Gain		108
Gross Unrealized (Loss)	(2,083)	(53)
Fair Value	46,390	51,687
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	20,350	16,302
Gross Unrealized Gain	13	918
Gross Unrealized (Loss)	(434)	(18)
Fair Value	$ 19,929	17,202
Foreign Bonds and Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		502
Gross Unrealized Gain		27
Fair Value		$ 529

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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