Debt Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Debt	$ 23,388	$ 23,337
Less current portion of long-term debt	(1,243)	(1,538)
Long-term debt	$ 22,145	$ 21,799
Current portion of long-term debt, Weighted Average Effective Interest Rate	3.60%	3.50%
Notes and debentures, due through 2097
Debt Instrument [Line Items]
Debt	$ 22,819	$ 22,719
Total Debt, Weighted Average Effective Interest Rate	4.70%	4.60%
Equipment obligations, due through 2028
Debt Instrument [Line Items]
Debt	$ 355	$ 378
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	$ 288	$ 298
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	$ (121)	$ (105)