Fair Value (Fair Value Measurements - Nonrecurring Fair Value Inputs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	1,559us-gaap_LoansReceivableHeldForSaleNet	$ 2,003us-gaap_LoansReceivableHeldForSaleNet
Consumer Loans Auto Financing Receivable [Member] \| Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Prepayment Rate	1.30%
Fair Value Inputs, Discount Rate	0.58%
Minimum [Member] \| Consumer Loans Auto Financing Receivable [Member] \| Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Loss Severity	0.00%
Maximum [Member] \| Consumer Loans Auto Financing Receivable [Member] \| Income Approach Valuation Technique [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Loss Severity	4.80%
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	1,561	1,554
Fair Value, Measurements, Nonrecurring [Member] \| Consumer Loans Auto Financing Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	1,500
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Consumer Loans Auto Financing Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans held-for-sale, net	1,500

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

+ References

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- Definition

Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

+ References

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- Definition

Amount classified as loans attributable to disposal group held for sale or disposed of. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph a

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 35

-Paragraph 49

-URI http://asc.fasb.org/extlink&oid=35742846&loc=d3e3084-111518

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section 30

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6490209&loc=d3e48214-111002

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