Loans and Allowance for Credit Losses, Troubled Debt Restructurings Modifications by Type (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Primary Modification Type [Abstract]
Principal	$ 411	$ 332
Interest rate reduction	623	522
Other interest rate concessions	2,466	1,829
Total	3,500	2,683
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	130	85
Weighted average interest rate reduction	3.29%	3.76%
Recorded investment related to interest rate reduction	891	783
Total Commercial [Member]
Primary Modification Type [Abstract]
Principal	39	5
Interest rate reduction	142	62
Other interest rate concessions	858	996
Total	1,039	1,063
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	10	11
Weighted average interest rate reduction	4.54%	1.79%
Recorded investment related to interest rate reduction	142	63
Commercial and Industrial Loans [Member]
Primary Modification Type [Abstract]
Principal	0	1
Interest rate reduction	67	8
Other interest rate concessions	327	401
Total	394	410
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	1	3
Weighted average interest rate reduction	7.60%	1.28%
Recorded investment related to interest rate reduction	67	9
Commercial Real Estate Mortgage [Member]
Primary Modification Type [Abstract]
Principal	24	4
Interest rate reduction	75	52
Other interest rate concessions	422	485
Total	521	541
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	5	0
Weighted average interest rate reduction	1.82%	1.90%
Recorded investment related to interest rate reduction	75	53
Commercial Real Estate Construction [Member]
Primary Modification Type [Abstract]
Principal	0	0
Interest rate reduction	0	2
Other interest rate concessions	109	107
Total	109	109
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	4	8
Weighted average interest rate reduction	0.00%	1.06%
Recorded investment related to interest rate reduction	0	1
Lease Financing [Member]
Primary Modification Type [Abstract]
Principal	0	0
Interest rate reduction	0	0
Other interest rate concessions	0	1
Total	0	1
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	0	0
Weighted average interest rate reduction	0.00%	0.00%
Recorded investment related to interest rate reduction	0	0
Foreign Loans [Member]
Primary Modification Type [Abstract]
Principal	15	0
Interest rate reduction	0	0
Other interest rate concessions	0	2
Total	15	2
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	0	0
Weighted average interest rate reduction	0.00%	0.00%
Recorded investment related to interest rate reduction	0	0
Total Consumer [Member]
Primary Modification Type [Abstract]
Principal	372	327
Interest rate reduction	481	460
Other interest rate concessions	1,608	833
Total	2,461	1,620
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	120	74
Weighted average interest rate reduction	3.06%	3.93%
Recorded investment related to interest rate reduction	749	720
Real estate 1-4 family first mortgage [Member]
Primary Modification Type [Abstract]
Principal	344	306
Interest rate reduction	379	297
Other interest rate concessions	1,381	199
Total	2,104	802
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	97	59
Weighted average interest rate reduction	2.43%	2.83%
Recorded investment related to interest rate reduction	623	540
Real estate 1-4 family junior lien mortgage [Member]
Primary Modification Type [Abstract]
Principal	27	19
Interest rate reduction	48	70
Other interest rate concessions	168	34
Total	243	123
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	15	9
Weighted average interest rate reduction	3.24%	4.02%
Recorded investment related to interest rate reduction	72	86
Credit Card [Member]
Primary Modification Type [Abstract]
Principal	0	0
Interest rate reduction	46	74
Other interest rate concessions	0	0
Total	46	74
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	0	0
Weighted average interest rate reduction	10.73%	10.88%
Recorded investment related to interest rate reduction	46	74
Automobile [Member]
Primary Modification Type [Abstract]
Principal	1	2
Interest rate reduction	6	19
Other interest rate concessions	24	22
Total	31	43
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	8	6
Weighted average interest rate reduction	6.39%	7.51%
Recorded investment related to interest rate reduction	6	20
Other revolving credit and installment [Member]
Primary Modification Type [Abstract]
Principal	0	0
Interest rate reduction	2	0
Other interest rate concessions	3	1
Total	5	1
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	0	0
Weighted average interest rate reduction	3.89%	0.00%
Recorded investment related to interest rate reduction	2	0
Trial modifications [Member]
Primary Modification Type [Abstract]
Principal	0	0
Interest rate reduction	0	0
Other interest rate concessions	32	577
Total	32	577
Financial effects of modifications [Abstract]
Charge-offs, financial effects of modifications	0	0
Weighted average interest rate reduction	0.00%	0.00%
Recorded investment related to interest rate reduction	$ 0	$ 0

Loans and Allowance for Credit Losses, Troubled Debt Restructurings Modifications by Type (Details) (USD $)
In Millions, unless otherwise specified

3 Months Ended

Mar. 31, 2013

Mar. 31, 2012

Primary Modification Type [Abstract]

Principal

$ 411

$ 332

Interest rate reduction

623

522

Other interest rate concessions