Securities - Impairment (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	$ 37,687	$ 83,040
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	104	1,435
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	11,028	42,155
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	146	1,528
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	48,715	125,195
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	250	2,963
U.S. government agencies [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	2,440	2,724
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	13	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	2,440	2,724
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	13	2
Commercial mortgage
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	1,159	837
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	8	53
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	312	0
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	5	0
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	1,471	837
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	13	53
Mortgage-backed securities [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	6,259	34,710
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	29	333
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	1,122	26,146
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	29	627
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	7,381	60,856
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	58	960
U.S. Treasury and government agencies [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	4,198	3,369
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	8	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	4,198	3,369
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	8	2
Obligations of U.S. states and municipalities [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	907	147
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	10	42
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	0	40
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	0	6
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	907	187
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	10	48
Certificates of Deposit [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	741	0
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	2	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	741	0
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	2	0
Non-U.S. government debt securities [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	14,527	11,901
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	21	66
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	1,927	1,286
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	4	15
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	16,454	13,187
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	25	81
Corporate Debt Securities [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	2,651	22,230
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	10	901
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	5,641	9,585
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	74	746
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	8,292	31,815
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	84	1,647
Collateralized Loan Obligations [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	6,328	5,610
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	17	49
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	2,063	3,913
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	35	117
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	8,391	9,523
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	52	166
Other, Debt Securities [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	2,076	4,735
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	7	40
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	275	1,185
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	4	17
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	2,351	5,920
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	11	57
Debt Securities [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	37,687	82,702
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	104	1,433
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	11,028	42,155
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	146	1,528
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	48,715	124,857
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	250	2,961
Equity securities [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	0	338
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	0	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	0	338
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	0	2
Residential Mortgage Backed Securities [Member] | Prime and Alt-A [Member]
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	218	649
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	2	12
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	76	970
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	1	206
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	294	1,619
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	3	218
Residential Mortgage Backed Securities [Member] | Subprime [Member]
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 Mortgage Backed Securities [Member] | Non-U.S.
Fair value and gross unrealized loss, securities impairment [Abstract]
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Fair Value	2,442	30,500
Available-for-sale Securities, with gross unrealized losses, Less than 12 Months, Gross unrealized losses	6	266
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Fair Value	734	25,176
Available-for-sale Securities, with gross unrealized losses, 12 Months or Longer, Gross unrealized losses	23	421
Available-for-sale securities, with gross unrealized losses, Fair Value, Total	3,176	55,676
Available-for-sale Securities, with gross unrealized losses, Gross Unrealized Losses	$ 29	$ 687