Derivative Instruments and Hedging Activities (Fair Value Amounts of Derivative Instruments Reported on our Condensed Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 41	$ 95
Derivative Liability, Fair Value, Gross Liability	43	95
Derivative, Notional Amount	29,434	34,166
Interest Receivable	470	476
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	20
Derivative Liability, Fair Value, Gross Liability	3	21
Derivative, Notional Amount	4,379	4,902
Interest Rate Swap [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	19
Derivative Liability, Fair Value, Gross Liability	0	21
Derivative, Notional Amount	4,225	4,731
Hedge notional amount associated with debt maturing in five or more years	3,300
Foreign Exchange Forward [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1
Derivative Liability, Fair Value, Gross Liability	3	0
Derivative, Notional Amount	154	171
Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	40	73
Derivative Liability, Fair Value, Gross Liability	39	73
Derivative, Notional Amount	24,913	29,172
Foreign Exchange Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Liability, Fair Value, Gross Liability	1	0
Derivative, Notional Amount	142	92
Equity Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1
Derivative Liability, Fair Value, Gross Liability	0	1
Derivative, Notional Amount	0	0
Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Receive-fixed Swaps, Fair Value, Gross Asset	0	8
Receive-fixed Swaps, Fair Value, Gross Liability	0	14
Receive-fixed Swaps, Notional Amount	3,300	1,700
Pay-fixed Swaps, Fair Value, Gross Asset	0	10
Pay-fixed Swaps, Fair Value, Gross Liability	0	1
Pay-fixed Swaps, Notional Amount	0	2,800
Cash Flow Hedging [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Pay-fixed Swaps, Fair Value, Gross Asset	0
Pay-fixed Swaps, Notional Amount	650
Interest Rate Swap [Member] \| Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	15	137
Foreign Exchange Forward [Member] \| Foreign Exchange Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Liability, Fair Value, Gross Liability	1	0
Derivative, Notional Amount	142	92
Futures and Forwards [Member] \| Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	103	0
Written Options [Member] \| Interest Rate Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	0
Derivative Liability, Fair Value, Gross Liability	39	73
Derivative, Notional Amount	12,449	14,518
Written Options [Member] \| Equity Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	1
Derivative, Notional Amount	0	0
Purchased Options [Member] \| Interest Rate Contract [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	39	73
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	12,346	14,517
Purchased Options [Member] \| Equity Contract [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	0	0
Other Trading [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	41	75
Derivative Liability, Fair Value, Gross Liability	40	74
Derivative, Notional Amount	25,055	29,264
Secured Debt [Member] \| Fair Value Hedging [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Receive-fixed Swaps, Fair Value, Gross Asset	0	0
Receive-fixed Swaps, Fair Value, Gross Liability	0	7
Receive-fixed Swaps, Notional Amount	240	240
Derivative assets in net asset position [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	39	87
Interest Receivable	0	7
Derivative assets in net liability positions [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	8
Interest Receivable	$ 0	$ 1

Hedge notional amount associated with debt maturing in five or more years

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- Definition

Pay-fixed Swaps on portfolios of held-for-investment automotive loan assets, Fair Value, Gross Asset

+ References

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Pay-fixed Swaps on portfolios of held-for-investment automotive loan assets, Fair Value, Gross Liability

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Pay-fixed Swaps on portfolios of held-for-investment automotive loan assets, Fair Value, Notional Amount

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Receive-fixed Swaps on Fixed-rate Debt Obligations, Fair Value, Gross Asset

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Receive-fixed Swaps on Fixed-rate Debt Obligations, Notional Amount

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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