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v3.23.1

Significant Accounting Policies (Details) - USD ($) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Mar. 31, 2023 | Mar. 31, 2022 | Mar. 31, 2023 | Mar. 31, 2022 | Sep. 30, 2022
Concentration Risk [Line Items] |  |  |  |  |
Restricted cash | $ 119,000 |  | $ 119,000 |  | $ 28,000
Restricted investments | 11,303,000 |  | 11,303,000 |  | 6,866,000
Debt securities, available-for-sale, intent impairments |  |  | 0 | $ 0 |
Debt securities, available-for-sale, allowance for credit loss | $ 0 | $ 0 | $ 0 | $ 0 |
Maximum |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Restricted cash |  |  |  |  | $ 100,000
Revenues | Customer Concentration Risk | Various Departments Of Transportation |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk percentage | 29.80% | 30.80% | 30.90% | 32.30% |
Revenues | Customer Concentration Risk | Florida Department of Transportation |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk percentage | 11.30% | 12.50% | 9.60% | 11.20% |
Private | Revenues | Customer Concentration Risk |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk percentage | 42.10% | 42.10% | 40.40% | 40.50% |
Public | Revenues | Customer Concentration Risk |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Concentration risk percentage | 57.90% | 57.90% | 59.60% | 59.50% |

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