Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Level 1 Available-for-sale Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 68,383	$ 67,842
Gross Unrealized Gain	1,610	1,971
Gross Unrealized (Loss)	(5)	(26)
Fair Value	69,988	69,787
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	695	1,152
Fair Value	695	1,152
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	43,907	42,032
Gross Unrealized Gain	204	229
Gross Unrealized (Loss)	(5)	(26)
Fair Value	44,106	42,235
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	20,797	21,666
Gross Unrealized Gain	1,337	1,660
Fair Value	22,134	23,326
Foreign Bonds and Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,984	2,992
Gross Unrealized Gain	69	82
Fair Value	$ 3,053	$ 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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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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