Loans and Leases (Impaired Loans) (Details) (Commercial Real Estate, USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	$ 195		$ 197
Unpaid principal balance with no related allowance recorded	292		322
Average recorded investment	195	238
Interest revenue recognized	4	5
CRE - property development
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	195	199	197
Unpaid principal balance with no related allowance recorded	222		224
Interest revenue with related allowance recognized	4	4
CRE - property development - acquired credit impaired
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	0		0
Unpaid principal balance with no related allowance recorded	34		34
CRE - other - acquired credit impaired
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	0	8	0
Unpaid principal balance with no related allowance recorded	36		64
Interest revenue with related allowance recognized	0	0
Recorded investment with related allowance	0	31
Interest revenue with no related allowance recognized	0	0
CRE - other
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	0	0
Interest revenue with related allowance recognized	$ 0	$ 1

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5258-111524

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- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

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- Definition

Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

+ References

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- Definition

Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

+ References

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Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

+ References

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- Definition

Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

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- Definition

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

+ References

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