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		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 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	$ 2	$ 20	$ 4	$ 33
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	4	45	5	75
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	4	21	12	62
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	2	4	4	13
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	6	8
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	7	5	24	18
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	$ 1	$ 1	$ 3	$ 2