Loans - Nature and Extent of Modfications (Details 4b) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Long-Term Credit Card Loan Modification Programs [Member]
Financing Receivable, Modifications [Line Items]
Loan modification program, customer fixed payment plan period (months)	60 months
Consumer Portfolio Segment | Consumer Loans Auto Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
New modifications	$ 17	$ 13
Consumer Portfolio Segment | Consumer business banking
Financing Receivable, Modifications [Line Items]
New modifications	13	56
Consumer Portfolio Segment | Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
New modifications	30	69
Consumer Portfolio Segment | Residential real estate, excluding PCI [Member]
Financing Receivable, Modifications [Line Items]
New modifications	511	1,807
Consumer Portfolio Segment | Home Equity Junior Lien [Member]
Financing Receivable, Modifications [Line Items]
New modifications	96	168
Consumer Portfolio Segment | Home Equity Senior Lien [Member]
Financing Receivable, Modifications [Line Items]
New modifications	12	37
Consumer Portfolio Segment | Prime Mortgages, including option ARMs [Member]
Financing Receivable, Modifications [Line Items]
New modifications	281	1,260
Consumer Portfolio Segment | Subprime Mortgage [Member]
Financing Receivable, Modifications [Line Items]
New modifications	122	342
Credit Card
Financing Receivable, Modifications [Line Items]
New modifications	511	881
Credit Card | Short-Term Credit Card Loan Modification Programs [Member]
Financing Receivable, Modifications [Line Items]
New modifications	31	55
Credit Card | Long-Term Credit Card Loan Modification Programs [Member]
Financing Receivable, Modifications [Line Items]
New modifications	$ 480	$ 826
Permanent Modification [Member] | Consumer Portfolio Segment | Residential real estate, excluding PCI [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	4,186	7,614
Interest rate reduction	85.00%	56.00%
Term or payment extensions	73.00%	69.00%
Principal and/or interest deferred	22.00%	13.00%
Principal forgiveness	19.00%	8.00%
Other	9.00%	51.00%
Permanent Modification [Member] | Consumer Portfolio Segment | Home Equity Junior Lien [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	1,816	2,699
Interest rate reduction	95.00%	97.00%
Term or payment extensions	69.00%	83.00%
Principal and/or interest deferred	20.00%	21.00%
Principal forgiveness	7.00%	21.00%
Other	7.00%	8.00%
Permanent Modification [Member] | Consumer Portfolio Segment | Home Equity Senior Lien [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	230	181
Interest rate reduction	63.00%	74.00%
Term or payment extensions	96.00%	80.00%
Principal and/or interest deferred	10.00%	6.00%
Principal forgiveness	22.00%	5.00%
Other	8.00%	41.00%
Permanent Modification [Member] | Consumer Portfolio Segment | Prime Mortgages, including option ARMs [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	950	3,981
Interest rate reduction	79.00%	20.00%
Term or payment extensions	82.00%	59.00%
Principal and/or interest deferred	36.00%	7.00%
Principal forgiveness	23.00%	0.00%
Other	19.00%	86.00%
Permanent Modification [Member] | Consumer Portfolio Segment | Subprime Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	1,190	753
Interest rate reduction	82.00%	84.00%
Term or payment extensions	68.00%	69.00%
Principal and/or interest deferred	13.00%	16.00%
Principal forgiveness	31.00%	5.00%
Other	3.00%	31.00%
Trial Modification [Member] | Consumer Portfolio Segment | Residential real estate, excluding PCI [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	1,338	593
Trial Modification [Member] | Consumer Portfolio Segment | Home Equity Junior Lien [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	209	76
Trial Modification [Member] | Consumer Portfolio Segment | Home Equity Senior Lien [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	92	101
Trial Modification [Member] | Consumer Portfolio Segment | Prime Mortgages, including option ARMs [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	485	129
Trial Modification [Member] | Consumer Portfolio Segment | Subprime Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of loans modified	552	287