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