Derivatives and Hedging Activities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Total fair value of derivative assets	$ 210	$ 765
Total fair value of derivative liabilities	218	280
Total derivatives assets, net	124	555
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset and liability netting	(80)	(157)
Total derivatives assets, net	124	555
Cash collateral netting, Assets	(6)	(54)
Other Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives assets, net	128	458
Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives assets, net	210	766
Other Assets [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives assets, net	11	111
Other Assets [Member] | Foreign exchange contracts [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives assets, net	117	347
Other Assets [Member] | Foreign exchange contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives assets, net	82	308
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative asset and liability netting	(80)	(157)
Total derivatives liabilities, net	93	55
Cash collateral netting, Liabilities	(45)	(68)
Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives liabilities, net	123	104
Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives liabilities, net	218	280
Other Liabilities [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives liabilities, net	34	69
Other Liabilities [Member] | Foreign exchange contracts [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives liabilities, net	89	35
Other Liabilities [Member] | Foreign exchange contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives liabilities, net	$ 95	$ 176