Derivatives and Hedging Activities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Total fair value of derivative assets	$ 622	$ 514
Total fair value of derivative liabilities	193	214
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset and liability netting	(131)	(90)
Total derivatives assets, net	210	396
Cash collateral netting, Assets	(281)	(28)
Other Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total fair value of derivative assets	479	256
Other Assets [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives assets, net	277	34
Other Assets [Member] | Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivatives assets, net	202	222
Other Assets [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total fair value of derivative assets	143	258
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative asset and liability netting	(131)	(90)
Total derivative liabilities, net	60	46
Cash collateral netting, Liabilities	(2)	(78)
Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total fair value of derivative liabilities	46	135
Other Liabilities [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivative liabilities, net	0	74
Other Liabilities [Member] | Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total derivative liabilities, net	46	61
Other Liabilities [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Total fair value of derivative liabilities	$ 147	$ 79