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
	Mar. 31, 2012	Mar. 31, 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	$ 13
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	30
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	8	41
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	9
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	5
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	17	13
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	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	$ 2	$ 1