Other Financial Information - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Sep. 30, 2024
Other Financials Information [Line Items]
Accrued contract costs including professional liability accruals	$ 1,379,800		$ 1,354,700
Restructuring expenses incurred	$ 0	$ 16,180
Accrued restructuring expenses		5,000
Cash dividends declared (in dollars per share)	$ 0.26
Accrued and unpaid dividend	$ 37,300
Labor-Related Costs
Other Financials Information [Line Items]
Restructuring expenses incurred		8,700
Non-Labor
Other Financials Information [Line Items]
Restructuring expenses incurred		$ 7,500
Professional Liability Accrual
Other Financials Information [Line Items]
Accrued contract costs including professional liability accruals	$ 833,000		$ 831,800