Balance Sheet Effect of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 31	$ 12
Derivative, Collateral, Obligation to Return Cash	11	15
Notional	96,676	99,856
Fair Value of Derivative Assets	982	909
Fair Value of Derivative Liabilities	420	166
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Notional	31,802	33,175
Not Designated as Hedging Instrument [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Notional	57,144	61,689
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Contract [Member]
Derivative [Line Items]
Notional	3,732	1,791
Not Designated as Hedging Instrument [Member] \| Cross Currency Interest Rate Contract [Member]
Derivative [Line Items]
Notional	3,998	3,201
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Derivative [Line Items]
Derivative Asset, Not Offset, Policy Election Deduction	226	113
Derivative Liability, Not Offset, Policy Election Deduction	226	113
Fair Value of Derivative Assets	982	909
Fair Value of Derivative Liabilities	420	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	323	487
Fair Value of Derivative Liabilities	132	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	227	156
Fair Value of Derivative Liabilities	119	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	62	24
Fair Value of Derivative Liabilities	147	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	370	242
Fair Value of Derivative Liabilities	$ 22	$ 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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