Debt Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Debt	$ 24,004	$ 23,425
Less current portion of long-term debt	(548)	(1,241)
Long-term debt	$ 23,456	$ 22,184
Current portion of long-term debt, Weighted Average Effective Interest Rate	6.40%	4.30%
Notes and debentures, due through 2097
Debt Instrument [Line Items]
Debt	$ 23,569	$ 22,919
Total Debt, Weighted Average Effective Interest Rate	4.90%	4.80%
Equipment obligations, due through 2028
Debt Instrument [Line Items]
Debt	$ 309	$ 332
Total Debt, Weighted Average Effective Interest Rate	3.60%	3.60%
Mortgage bonds, due through 2047
Debt Instrument [Line Items]
Debt	$ 47	$ 47
Total Debt, Weighted Average Effective Interest Rate	3.10%	3.10%
Financing obligations, due through 2053
Debt Instrument [Line Items]
Debt	$ 251	$ 268
Total Debt, Weighted Average Effective Interest Rate	4.50%	4.60%
Unamortized fair value adjustment under acquisition method accounting, discount, debt issuance costs, and other, net
Debt Instrument [Line Items]
Debt	$ (172)	$ (141)