Income Effect of Derivative Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 185	$ 237	$ 309	$ 315
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Net interest settlements and accruals excluded from the assessment of hedge effectiveness	94	79	271	220
Gain (Loss) on Interest Rate Fair Value Hedge Ineffectiveness	10	(2)	6	8
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	373	(88)	345	179
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(363)	86	(339)	(171)
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(22)	(10)	(83)	(37)
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	40	52	40	22
Not Designated as Hedging Instrument [Member] | Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 63	$ 118	$ 75	$ 102