Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 68,951	$ 67,842
Gross Unrealized Gain	1,053	1,971
Gross Unrealized (Loss)	(71)	(26)
Fair Value	69,933	69,787
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	515	1,152
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	0	0
Fair Value	515	1,152
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	51,632	42,032
Gross Unrealized Gain	108	229
Gross Unrealized (Loss)	(53)	(26)
Fair Value	51,687	42,235
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16,302	21,666
Gross Unrealized Gain	918	1,660
Gross Unrealized (Loss)	(18)
Fair Value	17,202	23,326
Foreign Bonds and Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	502	2,992
Gross Unrealized Gain	27	82
Gross Unrealized (Loss)	0	0
Fair Value	$ 529	$ 3,074

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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