Debt (Credit Facilities) (Details)	3 Months Ended
	Jun. 30, 2025 USD ($)	Mar. 31, 2025 borrowing	Sep. 30, 2024 USD ($)
Saudi Riyal Loan Facility Variable Rate Seven Point Three Five Percent | Blue Hydrogen Industrial Gases Company
Debt Instrument [Line Items]
Number of instruments derecognized | borrowing		2
Saudi Riyal Loan Facility Variable Rate Seven Point Three Five Percent | Bonds
Debt Instrument [Line Items]
Interest rate, variable percentage			7.35%
Long-term debt, principal amount			$ 451,100,000
Saudi Riyal Loan Facility Variable Rate Two Point Zero Percent | Blue Hydrogen Industrial Gases Company
Debt Instrument [Line Items]
Number of instruments derecognized | borrowing		2
Saudi Riyal Loan Facility Variable Rate Two Point Zero Percent | Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage			2.00%
Long-term debt, principal amount			$ 222,200,000
Revolving credit agreement | 364-Day Agreement | Line of Credit
Debt Instrument [Line Items]
Debt instrument term	364 days
Maximum borrowing capacity	$ 500,000,000
Credit facility, amount borrowed and outstanding	$ 0
Revolving credit agreement | Credit Agreement 2024 | Line of Credit
Debt Instrument [Line Items]
Debt instrument term	5 years
Maximum borrowing capacity	$ 3,000,000,000
Credit facility, amount borrowed and outstanding	0
Foreign credit facilities | Credit facilities of foreign subsidiaries
Debt Instrument [Line Items]
Maximum borrowing capacity	420,800,000		1,200,000,000
Credit facility, amount borrowed and outstanding	$ 420,800,000		$ 1,100,000,000