Income Effect of Derivative Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 296	$ 205
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	99	88
Ineffectiveness	17	6
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	610	221
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(593)	(215)
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(48)	(43)
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	33	65
Not Designated as Hedging Instrument [Member] | Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 195	$ 89