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Details of Selected Financial Statement Captions - Accounts Receivables (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Sep. 30, 2024
--- | --- | ---
Condensed Balance Sheet Statements, Captions [Line Items] |  |
Total accounts receivable | $ 420,768 | $ 402,938
Less: allowance for uncollectible accounts | (45,259) | (37,056)
Net accounts receivable | 375,509 | 365,882
Billed and Unbilled Receivables | Billed accounts receivable |  |
Condensed Balance Sheet Statements, Captions [Line Items] |  |
Total accounts receivable | 213,651 | 220,869
Billed and Unbilled Receivables | Unbilled revenue |  |
Condensed Balance Sheet Statements, Captions [Line Items] |  |
Total accounts receivable | 140,651 | 123,550
Insurance receivable |  |
Condensed Balance Sheet Statements, Captions [Line Items] |  |
Total accounts receivable | 22,940 | 51,715
Other accounts receivable |  |
Condensed Balance Sheet Statements, Captions [Line Items] |  |
Total accounts receivable | $ 43,526 | $ 6,804

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