Fair Value Measurements (Fair Value Hierarchy Classification) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term borrowings	$ 1,077	$ 601
Portion at Other than Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	147	127
Customer financing notes receivable	430	437
Short-term borrowings	1,077	601
Long-term debt (excluding capitalized leases)	26,161	23,280
Long-term liabilities	363	457
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	139	121
Customer financing notes receivable	414	420
Short-term borrowings	1,077	601
Long-term debt (excluding capitalized leases)	28,052	25,110
Long-term liabilities	331	427
Fair Value Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	0
Customer financing notes receivable	0
Short-term borrowings	0
Long-term debt (excluding capitalized leases)	0
Long-term liabilities	0
Fair Value Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	139
Customer financing notes receivable	414
Short-term borrowings	943
Long-term debt (excluding capitalized leases)	27,827
Long-term liabilities	331
Fair Value Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	0
Customer financing notes receivable	0
Short-term borrowings	134
Long-term debt (excluding capitalized leases)	225
Long-term liabilities	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	120	987
Derivative Assets	390	170
Derivative Liabilities	90	354
Fair Value, Measurements, Recurring [Member] | Fair Value Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	120	987
Derivative Assets	0	0
Derivative Liabilities	0	0
Fair Value, Measurements, 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	0
Derivative Assets	390	170
Derivative Liabilities	90	354
Fair Value, Measurements, 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	0
Derivative Assets	0	0
Derivative Liabilities	$ 0	$ 0