Balance Sheet Effect of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 16	$ 12
Derivative, Collateral, Obligation to Return Cash	10	15
Notional	96,740	99,856
Fair Value of Derivative Assets	979	909
Fair Value of Derivative Liabilities	216	166
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Notional	34,958	33,175
Not Designated as Hedging Instrument [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Notional	53,968	61,689
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Contract [Member]
Derivative [Line Items]
Notional	3,896	1,791
Not Designated as Hedging Instrument [Member] \| Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Notional	3,918	3,201
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Derivative [Line Items]
Derivative Asset, Not Offset, Policy Election Deduction	138	113
Derivative Liability, Not Offset, Policy Election Deduction	138	113
Fair Value of Derivative Assets	979	909
Fair Value of Derivative Liabilities	216	166
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Fair Value of Derivative Assets	429	487
Fair Value of Derivative Liabilities	83	80
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Not Designated as Hedging Instrument [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Fair Value of Derivative Assets	180	156
Fair Value of Derivative Liabilities	55	74
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Not Designated as Hedging Instrument [Member] \| Foreign Exchange Contract [Member]
Derivative [Line Items]
Fair Value of Derivative Assets	32	24
Fair Value of Derivative Liabilities	72	4
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Not Designated as Hedging Instrument [Member] \| Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Fair Value of Derivative Assets	338	242
Fair Value of Derivative Liabilities	$ 6	$ 8

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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