Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 67,842	$ 57,461
Gross Unrealized Gain	1,971	1,032
Gross Unrealized (Loss)	(26)	(3)
Fair Value	69,787	58,490
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,152	509
Fair Value	1,152	509
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	42,032	29,055
Gross Unrealized Gain	229	198
Gross Unrealized (Loss)	(26)	(3)
Fair Value	42,235	29,250
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	21,666	23,831
Gross Unrealized Gain	1,660	773
Fair Value	23,326	24,604
Foreign Bonds and Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,992	4,066
Gross Unrealized Gain	82	61
Fair Value	$ 3,074	$ 4,127

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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Amount, before tax, of unrealized loss 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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Amortized cost of 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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Amount of 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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