Loans - Financial Effects of Modifications and Redefaults (Details 4c) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Wholesale
Financing Receivable, Modifications [Line Items]
Weighted-average remaining term (in years) of all loans modified - after TDR	4.1	2.6
Loans that redefaulted within one year of modification	$ 47	$ 42
Average term extension granted on new TDRs	0.9	2.3
Consumer Portfolio Segment | Consumer Loans Auto Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	9.98%	11.69%
Weighted-average interest rate of loans with interest rate reductions - after TDR	4.46%	5.57%
Consumer Portfolio Segment | Consumer business banking
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	7.96%	7.33%
Weighted-average interest rate of loans with interest rate reductions - after TDR	6.15%	5.54%
Weighted-average remaining term (in years) of all loans modified - before TDR	1.4	1.5
Weighted-average remaining term (in years) of all loans modified - after TDR	3.5	2.9
Loans that redefaulted within one year of modification	11	24
Credit Card
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	16.46%	16.35%
Weighted-average interest rate of loans with interest rate reductions - after TDR	5.52%	5.27%
Number of loans that redefaulted within one year of modification	35.72%		35.47%
Loans that redefaulted within one year of modification	97	199
Permanent Modification [Member] | Consumer Portfolio Segment | Home Equity Senior Lien [Member]
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	6.93%	7.33%
Weighted-average interest rate of loans with interest rate reductions - after TDR	3.39%	3.37%
Weighted-average remaining term (in years) of loans with term or payment extensions - before TDR	20	17
Financing Receivable, Modifications, Post-Modification, Weighted-Average Remaining Term of Financing Receivables With Term Or Payment Extensions	29	29
Weighted-average remaining term (in years) of loans with term or payment extensions - after TDR	6.7
Charge-offs recognized upon modification	1	0
Principal deferred	1	0
Principal forgiven	3	0
Number of loans that redefaulted within one year of modification	20.00%
Loans that redefaulted within one year of modification	5	4
Financing Receivable, Modifications, Subsequent Default Occurred, Number of Contracts	68	40
Permanent Modification [Member] | Consumer Portfolio Segment | Home Equity Junior Lien [Member]
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	5.63%	5.38%
Weighted-average interest rate of loans with interest rate reductions - after TDR	1.67%	1.35%
Weighted-average remaining term (in years) of loans with term or payment extensions - before TDR	21	21
Financing Receivable, Modifications, Post-Modification, Weighted-Average Remaining Term of Financing Receivables With Term Or Payment Extensions	33	35
Weighted-average remaining term (in years) of loans with term or payment extensions - after TDR	6.6
Charge-offs recognized upon modification	6	35
Principal deferred	8	9
Principal forgiven	4	19
Number of loans that redefaulted within one year of modification	15.00%
Loans that redefaulted within one year of modification	16	6
Financing Receivable, Modifications, Subsequent Default Occurred, Number of Contracts	411	182
Permanent Modification [Member] | Consumer Portfolio Segment | Prime Mortgages, including option ARMs [Member]
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	5.90%	6.12%
Weighted-average interest rate of loans with interest rate reductions - after TDR	2.59%	2.88%
Weighted-average remaining term (in years) of loans with term or payment extensions - before TDR	26	25
Financing Receivable, Modifications, Post-Modification, Weighted-Average Remaining Term of Financing Receivables With Term Or Payment Extensions	36	31
Weighted-average remaining term (in years) of loans with term or payment extensions - after TDR	9.1
Charge-offs recognized upon modification	14	18
Principal deferred	52	27
Principal forgiven	35	1
Number of loans that redefaulted within one year of modification	12.00%
Loans that redefaulted within one year of modification	67	89
Financing Receivable, Modifications, Subsequent Default Occurred, Number of Contracts	248	316
Permanent Modification [Member] | Consumer Portfolio Segment | Subprime Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	8.17%	8.25%
Weighted-average interest rate of loans with interest rate reductions - after TDR	3.72%	3.73%
Weighted-average remaining term (in years) of loans with term or payment extensions - before TDR	24	24
Financing Receivable, Modifications, Post-Modification, Weighted-Average Remaining Term of Financing Receivables With Term Or Payment Extensions	32	35
Weighted-average remaining term (in years) of loans with term or payment extensions - after TDR	7.3
Charge-offs recognized upon modification	5	3
Principal deferred	13	11
Principal forgiven	43	3
Number of loans that redefaulted within one year of modification	25.00%
Loans that redefaulted within one year of modification	41	107
Financing Receivable, Modifications, Subsequent Default Occurred, Number of Contracts	374	685
Permanent Modification [Member] | Consumer Portfolio Segment | Residential real estate, excluding PCI [Member]
Financing Receivable, Modifications [Line Items]
Weighted-average interest rate of loans with interest rate reductions - before TDR	6.55%	6.50%
Weighted-average interest rate of loans with interest rate reductions - after TDR	2.79%	2.75%
Weighted-average remaining term (in years) of loans with term or payment extensions - before TDR	25	24
Financing Receivable, Modifications, Post-Modification, Weighted-Average Remaining Term of Financing Receivables With Term Or Payment Extensions	34	32
Charge-offs recognized upon modification	26	56
Principal deferred	74	47
Principal forgiven	85	23
Loans that redefaulted within one year of modification	$ 129	$ 206
Financing Receivable, Modifications, Subsequent Default Occurred, Number of Contracts	1,101	1,223
Trial Modifications Since Mid 2010 [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Trial Modifications Successfully Converted to Permanent Modifications	85.00%