Indebtedness: (Schedule of Long-Term Debt) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Finance leases, average interest rate	4.223%
Finance leases	$ 88	$ 84
Long-term debt, including current maturities	46,255	48,667
Less current portion of long-term debt	2,447	3,533
Long-term debt	$ 43,808	45,134
U.S. Dollar Notes
Debt Instrument [Line Items]
Average interest rate	4.653%
Long-term debt, including current maturities	$ 36,660	37,430
U.S. Dollar Notes | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage	0.875%
U.S. Dollar Notes | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage	6.375%
Euro Notes | Euro notes
Debt Instrument [Line Items]
Average interest rate	2.039%
Long-term debt, including current maturities	$ 6,606	7,942
Euro Notes | Euro notes | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage	0.125%
Euro Notes | Euro notes | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage	3.75%
Euro Bank Loan | Euro notes
Debt Instrument [Line Items]
Average interest rate	2.597%
Long-term debt, including current maturities	$ 2,873	2,944
Swedish Krona Notes | Euro notes
Debt Instrument [Line Items]
Average interest rate	2.19%
Long-term debt, including current maturities	$ 28	$ 267