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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

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- Definition 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). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
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