Securitizations and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Variable Interest Entity [Line Items]
Assets of nonconsolidated variable interest entities	$ 3,571		$ 2,899
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	4,345		3,574
Carrying value of assets for VIEs for which we have continuing involvement	34,329		37,631
Carrying value of liabilities for VIEs for which we have continuing involvement	13,612		13,490
Retained notes and certificated residual interest	53
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale, Gain (Loss) on Sale	2	$ 0
Commercial Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	505		460
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	205		169
Assets of nonconsolidated variable interest entities	0		0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	695		651
Automobile Loan [Member] \| Consumer Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	19,632		20,869
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	8,298		8,557
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	79		24
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	0		0
Assets of nonconsolidated variable interest entities	3,571		2,899
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	3,650		2,923
Automobile Loan [Member] \| Consumer Portfolio Segment [Member] \| Held-to-maturity Securities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	52
Automobile Loan [Member] \| Consumer Portfolio Segment [Member] \| Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	27
Automobile Loan [Member] \| Commercial Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	14,113		16,278
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	5,109		4,764
Unencumbered [Member] \| Automobile Loan [Member] \| Consumer Portfolio Segment [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	9,200		9,600
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 64		$ 50

Assets of nonconsolidated variable interest entities

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- Definition

The carrying amount of the assets in the reporting entity's statement of financial position that relate to consolidated and nonconsolidated Variable Interest Entities.

+ References

No definition available.

+ Details

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- Definition

Carrying value of liabilities for VIEs for which we have continuing involvement

+ References

No definition available.

+ Details

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- Definition

Retained notes and certificated residual interest

+ References

No definition available.

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- Definition

Reflects, by transferred financial asset type, the amount of sales proceeds in excess of or deficient from the sum of the carrying amounts of transferred financial assets plus transaction costs, including those transactions in which the seller/transferor has continuing involvement with the financial assets that have been transferred.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 10
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=65892426&loc=d3e96813-111708

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- Definition

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5710-111685

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- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5728-111685

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5747-111685

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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.

+ References

No definition available.

+ Details

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- Definition

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

+ Details

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- Definition

Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

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