Derivative Instruments and Hedging Activities (Assets and LIabilities - Designated vs. Not Designated Hedging Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Total asset derivatives	$ 348	$ 376
Total liability derivatives	315	424
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	57	51
Total liability derivatives	138	358
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	291	325
Total liability derivatives	177	66
Interest Rate Contract
Derivatives, Fair Value [Line Items]
Total asset derivatives	15	18
Total liability derivatives	262	300
Interest Rate Contract | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	15	18
Total liability derivatives	125	295
Interest Rate Contract | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	0	0
Total liability derivatives	137	5
Cross Currency Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	29	4
Total liability derivatives	3	18
Cross Currency Interest Rate Contract [Member] | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	29	4
Total liability derivatives	3	18
Cross Currency Interest Rate Contract [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	0	0
Total liability derivatives	0	0
Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	269	309
Total liability derivatives	30	64
Foreign Exchange Contract [Member] | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	8	9
Total liability derivatives	1	19
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	261	300
Total liability derivatives	29	45
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Total asset derivatives	35	45
Total liability derivatives	20	42
Commodity Contract [Member] | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	5	20
Total liability derivatives	9	26
Commodity Contract [Member] | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total asset derivatives	30	25
Total liability derivatives	$ 11	$ 16