Loans and ACL (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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	$ 1	$ 2	$ 3	$ 4
Commercial Real Estate - Other [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	6	4	6	5
Commercial Real Estate - Residential ADC [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	3	4	4	12
Direct Retail Lending [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	1	2	2	4
Retail Revolving Credit [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	2	3	5	6
Retail Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	4	7	12	24
Retail Sales Finance [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	1		1
Retail Other Lending Subsidiaries [Member]
Financing Receivable, Modifications [Line Items]
Modifications that defaulted during the period that had been classified as a TDR during the previous 12 months	$ 6	$ 1	$ 12	$ 3