Fair Value Measurements (Fair Value Hierarchy Classification) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term borrowings	$ 1,200	$ 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	143	127
Customer financing notes receivable	450	437
Short-term borrowings	1,200	600
Long-term debt (excluding capitalized leases)	23,361	23,280
Long-term liabilities	433	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	134	121
Customer financing notes receivable	428	420
Short-term borrowings	1,200	600
Long-term debt (excluding capitalized leases)	25,154	25,110
Long-term liabilities	407	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	134
Customer financing notes receivable	428
Short-term borrowings	1,074
Long-term debt (excluding capitalized leases)	24,975
Long-term liabilities	407
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	126
Long-term debt (excluding capitalized leases)	179
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	316	987
Derivative Assets	106	170
Derivative Liabilities	241	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	316	987
Derivative Assets	2	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	104	170
Derivative Liabilities	241	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