Allowance for Credit Losses (Summary of the pre-default balance for modifications that experienced a payment default) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	$ 0	$ 5	$ 4	$ 38
Commercial Real Estate - Other [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	1	4	6	79
Commercial Real Estate - Residential ADC [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	1	11	13	73
Direct Retail Lending [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	3	1	7	14
Retail Revolving Credit [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	3	3	9	11
Retail Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	6	5	30	23
Retail Sales Finance [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	0	0	0	1
Retail Other Lending Subsidiaries [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a restructuring during the previous 12 months	$ 5	$ 2	$ 8	$ 4