Variable Interest Entities (JIGPC Joint Venture) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Sep. 30, 2025	Sep. 30, 2024
Schedule of Equity Method Investments [Line Items]
Investments in net assets of an advances to equity affiliates		$ 5,366.1	$ 4,792.5
Jazan Integrated Gasification and Power Company ("JIGPC")
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage		55.00%
Ownership percentage attributable to noncontrolling partner (in percent)		4.00%
Investment balance		$ 3,100.0	$ 2,900.0
Investments in net assets of an advances to equity affiliates		$ 115.0
Jazan Integrated Gasification and Power Company ("JIGPC") | Aramco
Schedule of Equity Method Investments [Line Items]
Term Of Project Agreement (in years)	25 years