Securities - Amortized Costs, Fair Value (Details 1) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	$ 373,308,000,000	$ 358,940,000,000
Available-for-sale Securities, Gross Unrealized Gains	9,787,000,000	8,804,000,000
Available-for-sale Securities, Gross Unrealized Losses	1,364,000,000	2,963,000,000
Available-for-sale Securities	381,731,000,000	364,781,000,000
Held-to-maturity Securities, Amortized Cost	11,000,000	12,000,000
Held-to-maturity Securities, Gross unrealized gains	1,000,000	1,000,000
Held-to-maturity Securities, Gross unrealized losses	0	0
Held-to-maturity Securities, Fair Value	12,000,000	13,000,000
U.S. government-sponsored enterprise obligations, fair values	86,000,000,000	89,300,000,000
Equity securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	2,486,000,000	2,693,000,000
Available-for-sale Securities, Gross Unrealized Gains	23,000,000	14,000,000
Available-for-sale Securities, Gross Unrealized Losses	4,000,000	2,000,000
Available-for-sale Securities	2,505,000,000	2,705,000,000
Debt Securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	370,822,000,000	356,247,000,000
Available-for-sale Securities, Gross Unrealized Gains	9,764,000,000	8,790,000,000
Available-for-sale Securities, Gross Unrealized Losses	1,360,000,000	2,961,000,000
Available-for-sale Securities	379,226,000,000	362,076,000,000
Mortgage-backed securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	187,396,000,000	180,838,000,000
Available-for-sale Securities, Gross Unrealized Gains	6,492,000,000	6,015,000,000
Available-for-sale Securities, Gross Unrealized Losses	462,000,000	960,000,000
Available-for-sale Securities	193,426,000,000	185,893,000,000
US Government Corporations and Agencies Securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	99,397,000,000	101,968,000,000
Available-for-sale Securities, Gross Unrealized Gains	4,923,000,000	5,141,000,000
Available-for-sale Securities, Gross Unrealized Losses	2,000,000	2,000,000
Available-for-sale Securities	104,318,000,000	107,107,000,000
Commercial mortgage
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	10,718,000,000	10,632,000,000
Available-for-sale Securities, Gross Unrealized Gains	852,000,000	650,000,000
Available-for-sale Securities, Gross Unrealized Losses	4,000,000	53,000,000
Available-for-sale Securities	11,566,000,000	11,229,000,000
Prime and Alt A [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	2,734,000,000	2,170,000,000
Available-for-sale Securities, Gross Unrealized Gains	60,000,000	54,000,000
Available-for-sale Securities, Gross Unrealized Losses	183,000,000	218,000,000
Available-for-sale Securities	2,611,000,000	2,006,000,000
Subprime [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	29,000,000	1,000,000
Available-for-sale Securities, Gross Unrealized Gains	0	0
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities	29,000,000	1,000,000
Non-U.S. [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	74,518,000,000	66,067,000,000
Available-for-sale Securities, Gross Unrealized Gains	657,000,000	170,000,000
Available-for-sale Securities, Gross Unrealized Losses	273,000,000	687,000,000
Available-for-sale Securities	74,902,000,000	65,550,000,000
U.S. Treasury and government agencies [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	11,657,000,000	8,184,000,000
Available-for-sale Securities, Gross Unrealized Gains	115,000,000	169,000,000
Available-for-sale Securities, Gross Unrealized Losses	5,000,000	2,000,000
Available-for-sale Securities	11,767,000,000	8,351,000,000
Obligations of U.S. states and municipalities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	17,840,000,000	15,404,000,000
Available-for-sale Securities, Gross Unrealized Gains	1,536,000,000	1,184,000,000
Available-for-sale Securities, Gross Unrealized Losses	34,000,000	48,000,000
Available-for-sale Securities	19,342,000,000	16,540,000,000
Certificates of Deposit [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	3,044,000,000	3,017,000,000
Available-for-sale Securities, Gross Unrealized Gains	2,000,000	0
Available-for-sale Securities, Gross Unrealized Losses	2,000,000	0
Available-for-sale Securities	3,044,000,000	3,017,000,000
Non-U.S. government debt securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	52,206,000,000	44,944,000,000
Available-for-sale Securities, Gross Unrealized Gains	534,000,000	402,000,000
Available-for-sale Securities, Gross Unrealized Losses	53,000,000	81,000,000
Available-for-sale Securities	52,687,000,000	45,265,000,000
Corporate Debt Securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	60,537,000,000	63,607,000,000
Available-for-sale Securities, Gross Unrealized Gains	476,000,000	216,000,000
Available-for-sale Securities, Gross Unrealized Losses	618,000,000	1,647,000,000
Available-for-sale Securities	60,395,000,000	62,176,000,000
Collateralized debt obligations, Asset Backed Securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	24,938,000,000	24,474,000,000
Available-for-sale Securities, Gross Unrealized Gains	455,000,000	553,000,000
Available-for-sale Securities, Gross Unrealized Losses	154,000,000	166,000,000
Available-for-sale Securities	25,239,000,000	24,861,000,000
Other, Debt Securities [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Amortized Cost	13,204,000,000	15,779,000,000
Available-for-sale Securities, Gross Unrealized Gains	154,000,000	251,000,000
Available-for-sale Securities, Gross Unrealized Losses	32,000,000	57,000,000
Available-for-sale Securities	13,326,000,000	15,973,000,000
Accumulated Other-than-Temporary Impairment [Member]
Amortized costs and estimated fair values
Available-for-sale Securities, Gross Unrealized Losses	$ 78,000,000	$ 91,000,000