Securities - Impairment (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	$ 47,950	$ 37,687
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	300	104
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	4,774	11,028
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	67	146
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	52,724	48,715
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	367	250
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	18,800	2,440
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	131	13
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	0
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	18,800	2,440
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	131	13
Commercial Mortgage Backed Securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	502	1,159
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	7	8
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	312
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	5
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	502	1,471
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	7	13
Collateralized Mortgage Backed Securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	20,671	6,259
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	143	29
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	266	1,122
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	10	29
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	20,937	7,381
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	153	58
US Treasury and Government
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	2,070	4,198
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	47	8
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	0
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	2,070	4,198
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	47	8
US States and Political Subdivisions Debt Securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	3,164	907
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	53	10
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	0
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	3,164	907
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	53	10
Certificates of Deposit
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	917	741
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	1	2
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	0
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	917	741
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	1	2
Foreign Government Debt Securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	13,279	14,527
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	23	21
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	1,511	1,927
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	3	4
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	14,790	16,454
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	26	25
Corporate Debt Securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	3,966	2,651
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	24	10
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	1,798	5,641
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	39	74
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	5,764	8,292
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	63	84
Collateralized loan obligations
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	2,348	6,328
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	6	17
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	942	2,063
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	13	35
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	3,290	8,391
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	19	52
Other Debt Obligations
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	1,535	2,076
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	3	7
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	257	275
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	2	4
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	1,792	2,351
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	5	11
Debt Securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	47,950	37,687
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	300	104
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	4,774	11,028
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	67	146
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	52,724	48,715
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	367	250
Equity securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	0
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	0	0
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	0	0
Residential and commercial mortgage securitizations | Prime and Alt-A
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	194	218
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	4	2
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	76
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	1
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	194	294
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	4	3
Residential and commercial mortgage securitizations | Subprime
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	0
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	0	0
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	0	0
Residential and commercial mortgage securitizations | Foreign Mortgage-backed Securities
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	1,175	2,442
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	1	6
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	266	734
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	10	23
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	1,441	3,176
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	$ 11	$ 29