Fair Value Measurements (Fair Value Hierarchy Classification) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
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	$ 267	$ 220
Short-term borrowings	(228)	(2,293)
Long-term debt (excluding finance leases)	(32,489)	(40,883)
Long-term liabilities	(28)	(334)
Short-term borrowings	(228)	(2,293)
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer financing notes receivable	259	220
Short-term borrowings	(228)	(2,293)
Long-term debt (excluding finance leases)	(37,503)	(45,887)
Long-term liabilities	(26)	(320)
Fair Value Level 1 [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer financing notes receivable	0	0
Short-term borrowings	0	0
Long-term debt (excluding finance leases)	0	0
Long-term liabilities	0	0
Fair Value Level 2 [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer financing notes receivable	259	220
Short-term borrowings	(160)	0
Long-term debt (excluding finance leases)	(29,236)	(45,802)
Long-term liabilities	(26)	(320)
Fair Value Level 3 [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Customer financing notes receivable	0	0
Short-term borrowings	(68)	(2,293)
Long-term debt (excluding finance leases)	(8,267)	(85)
Long-term liabilities	0	0
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		53
Marketable securities held in trusts	847	0
Derivative assets	54	46
Derivative liabilities	(255)	(282)
Fair Value, Recurring [Member] | Fair Value Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		53
Marketable securities held in trusts	840
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Recurring [Member] | Fair Value Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0
Marketable securities held in trusts	7
Derivative assets	54	46
Derivative liabilities	(255)	(282)
Fair Value, Recurring [Member] | Fair Value Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		0
Marketable securities held in trusts	0
Derivative assets	0	0
Derivative liabilities	$ 0	$ 0