Income Effect of Derivative Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 280	$ 185	$ 835	$ 309
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	95	94	292	271
Ineffectiveness	(1)	10	21	6
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(228)	373	655	345
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	227	(363)	(634)	(339)
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	21	(22)	(70)	(83)
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	37	40	129	40
Not Designated as Hedging Instrument [Member] | Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 128	$ 63	$ 463	$ 75