Fair Value Measurements (Fair Value Hierarchy Classification) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Portion at Other than Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer financing notes receivable	$ 66	$ 74
Long-term debt (excluding finance leases)	42,588	43,546
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities held in trusts	705	745
Derivative assets	195	308
Derivative liabilities	212	180
Customer financing notes receivable	56	63
Long-term debt (excluding finance leases)	39,957	41,598
Marketable securities held in trusts	705	745
Fair Value Level 1 [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities held in trusts	646	682
Derivative assets	0	0
Derivative liabilities	0	0
Customer financing notes receivable	0	0
Long-term debt (excluding finance leases)	0	0
Fair Value Level 2 [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities held in trusts	59	63
Derivative assets	195	308
Derivative liabilities	212	180
Customer financing notes receivable	56	63
Long-term debt (excluding finance leases)	35,914	37,559
Fair Value Level 3 [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities held in trusts	0	0
Derivative assets	0	0
Derivative liabilities	0	0
Customer financing notes receivable	0	0
Long-term debt (excluding finance leases)	$ 4,043	$ 4,039