Allowance for Credit Losses (Breakdown of Recorded Investment in Loans Based on the Method for Determining Allowance) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Individually Evaluated for Impairment	$ 2,730	$ 2,747
Collectively Evaluated for Impairment	111,466	111,856
Commercial and Industrial [Member]
Individually Evaluated for Impairment	615	631
Collectively Evaluated for Impairment	37,814	37,664
Commercial Real Estate - Other [Member]
Individually Evaluated for Impairment	291	312
Collectively Evaluated for Impairment	11,134	11,149
Commercial Real Estate - Residential ADC [Member]
Individually Evaluated for Impairment	123	155
Collectively Evaluated for Impairment	1,052	1,106
Commercial Other Lending Subsidiaries [Member]
Individually Evaluated for Impairment	3	3
Collectively Evaluated for Impairment	4,021	4,135
Direct Retail Lending [Member]
Individually Evaluated for Impairment	233	235
Collectively Evaluated for Impairment	15,534	15,582
Retail Revolving Credit [Member]
Individually Evaluated for Impairment	55	56
Collectively Evaluated for Impairment	2,229	2,274
Retail Residential Mortgage [Member]
Individually Evaluated for Impairment	1,202	1,187
Collectively Evaluated for Impairment	22,752	23,085
Retail Sales Finance [Member]
Individually Evaluated for Impairment	23	22
Collectively Evaluated for Impairment	8,091	7,714
Retail Other Lending Subsidiaries [Member]
Individually Evaluated for Impairment	185	146
Collectively Evaluated for Impairment	5,834	5,853
Covered [Member]
Collectively Evaluated for Impairment	$ 3,005	$ 3,294