Debt and Credit Agreements - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Finance Leases Average Interest Rate	5.90%
Subtotal Long-term Debt (Including Current Portion)	$ 18,533	$ 18,047
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Long-term Debt (Excluding Current Portion)	Long-term Debt (Excluding Current Portion)
Finance Leases	$ 17	$ 29
Less Debt Due within One Year	(558)	(151)
Long-term Debt (Excluding Current Portion)	$ 17,975	17,896
Notes
Debt Instrument [Line Items]
Debt Average Interest Rates	4.20%
Subtotal Long-term Debt (Including Current Portion)	$ 18,514	17,877
Equipment Obligations
Debt Instrument [Line Items]
Debt Average Interest Rates	4.40%
Subtotal Long-term Debt (Including Current Portion)	$ 2	$ 141