Allowance for Credit Losses (Summary of the pre-default balance for modifications that experienced a payment default) (Details) (USD $) In Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2011
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	$ 5	$ 38
Commercial Real Estate - Other [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	4	79
Commercial Real Estate - Residential ADC [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	11	73
Commercial Specialized Lending [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	0	0
Direct Retail Lending [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	1	14
Retail Revolving Credit [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	3	11
Retail Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	5	23
Retail Sales Finance [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	0	1
Retail Specialized Lending [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted in the current period that were modified in the prior 12 months	$ 2	$ 4