Allowance for Credit Losses (Summary of the primary reason loan modifications were classified as restructurings) (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]
Rate	$ 5	[1],[2]	$ 12	[1],[2]
Structure	28	[2]	13	[2]
Increase To Allowance	0		1
Commercial Real Estate - Other [Member]
Financing Receivable, Modifications [Line Items]
Rate	4	[1],[2]	19	[1],[2]
Structure	9	[2]	13	[2]
Increase To Allowance	1		1
Commercial Real Estate - Residential ADC [Member]
Financing Receivable, Modifications [Line Items]
Rate	0	[1],[2]	12	[1],[2]
Structure	13	[2]	9	[2]
Increase To Allowance	0		3
Direct Retail Lending [Member]
Financing Receivable, Modifications [Line Items]
Rate	6	[1],[2]	16	[1],[2]
Structure	2	[2]	1	[2]
Increase To Allowance	1		3
Retail Revolving Credit [Member]
Financing Receivable, Modifications [Line Items]
Rate	8	[1],[2]	11	[1],[2]
Structure	0	[2]	0	[2]
Increase To Allowance	2		2
Retail Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Rate	55	[1],[2]	32	[1],[2]
Structure	9	[2]	5	[2]
Increase To Allowance	3		5
Retail Sales Finance [Member]
Financing Receivable, Modifications [Line Items]
Rate	2	[1],[2]	1	[1],[2]
Structure	0	[2]	2	[2]
Increase To Allowance	0		0
Retail Other Lending Subsidiaries [Member]
Financing Receivable, Modifications [Line Items]
Rate	8	[1],[2]	12	[1],[2]
Structure	2	[2]	1	[2]
Increase To Allowance	$ 4		$ 4

[1] Includes restructurings made with a below market interest rate that also includes a modification of loan structure.

[2] Includes modifications made to existing restructurings, as well as new modifications that are considered restructurings. Balances represent the recorded investment as of the end of the period in which the modification was made.