Debt Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Debt	$ 23,425	$ 23,388
Less current portion of long-term debt	(1,241)	(1,243)
Long-term debt	$ 22,184	$ 22,145
Current portion of long-term debt, Weighted Average Effective Interest Rate	4.30%	3.60%
Notes and debentures, due through 2097
Debt Instrument [Line Items]
Debt	$ 22,919	$ 22,819
Total Debt, Weighted Average Effective Interest Rate	4.80%	4.70%
Equipment obligations, due through 2028
Debt Instrument [Line Items]
Debt	$ 332	$ 355
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	$ 268	$ 288
Total Debt, Weighted Average Effective Interest Rate	4.60%	4.60%
Unamortized fair value adjustment under acquisition method accounting, discount, debt issuance costs, and other, net
Debt Instrument [Line Items]
Debt	$ (141)	$ (121)