FAIR VALUE MEASUREMENTS (Details 4) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	$ 6,460,000,000	$ 5,618,000,000	$ 9,374,000,000	$ 6,380,000,000
Sales, assets	(645,000,000)	(340,000,000)	(1,203,000,000)	(404,000,000)
Settlements, assets	(1,335,000,000)	(1,595,000,000)	(3,887,000,000)	(2,980,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	4,480,000,000	3,683,000,000	4,284,000,000	2,996,000,000
Securities purchased through FRBNY's auction of Maiden Lane III assets	5,000,000,000		5,000,000,000
Fair value of additional securities purchase through additional auctions of Maiden Lane III assets	2,100,000,000		2,100,000,000
Transfers into Level 3 at end of reporting period, net gains (losses) not included in realized and unrealized gains and losses related to Level 3 for the period	(11,000,000)		47,000,000
Transfers out Level 3 at end of reporting period, net gains (losses) not included in realized and unrealized gains and losses related to Level 3 for the period.	30,000,000		57,000,000
Liabilities
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, liabilities			2,000,000	39,000,000
Sales, liabilities	(8,000,000)	(10,000,000)	(14,000,000)	(19,000,000)
Settlements, liabilities	(738,000,000)	173,000,000	493,000,000	277,000,000
Purchases, Sales, Issues and Settlements, Net, liabilities	(746,000,000)	163,000,000	481,000,000	297,000,000
Policyholder contract deposits
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Sales, liabilities	(8,000,000)	(10,000,000)	(14,000,000)	(19,000,000)
Settlements, liabilities	10,000,000	6,000,000	13,000,000	12,000,000
Purchases, Sales, Issues and Settlements, Net, liabilities	2,000,000	(4,000,000)	(1,000,000)	(7,000,000)
Derivative liabilities, net
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, liabilities			2,000,000	39,000,000
Settlements, liabilities	(770,000,000)	(28,000,000)	344,000,000	9,000,000
Purchases, Sales, Issues and Settlements, Net, liabilities	(770,000,000)	(28,000,000)	346,000,000	48,000,000
Other long-term debt
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Settlements, liabilities	22,000,000	195,000,000	136,000,000	256,000,000
Purchases, Sales, Issues and Settlements, Net, liabilities	22,000,000	195,000,000	136,000,000	256,000,000
Bonds available for sale
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	1,175,000,000	5,078,000,000	3,699,000,000	5,723,000,000
Sales, assets	(548,000,000)	(11,000,000)	(721,000,000)	(43,000,000)
Settlements, assets	(900,000,000)	(1,177,000,000)	(1,749,000,000)	(2,056,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	(273,000,000)	3,890,000,000	1,229,000,000	3,624,000,000
Bonds available for sale | Obligations of states, municipalities and political subdivisions
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	97,000,000	63,000,000	205,000,000	176,000,000
Sales, assets	(158,000,000)		(166,000,000)
Settlements, assets	(2,000,000)	(1,000,000)	(2,000,000)	(2,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	(63,000,000)	62,000,000	37,000,000	174,000,000
Bonds available for sale | Non-U.S. government
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	1,000,000	1,000,000	1,000,000	1,000,000
Sales, assets	(1,000,000)	(1,000,000)	(3,000,000)	(1,000,000)
Purchases, Sales, Issues and Settlements, Net, assets			(2,000,000)
Bonds available for sale | Corporate debt
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	80,000,000	412,000,000	141,000,000	420,000,000
Sales, assets	(52,000,000)	19,000,000	(53,000,000)
Settlements, assets	(23,000,000)	(126,000,000)	(86,000,000)	(148,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	5,000,000	305,000,000	2,000,000	272,000,000
Bonds available for sale | Residential mortgage backed securities (RMBS)
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	198,000,000	4,307,000,000	2,110,000,000	4,624,000,000
Sales, assets	(268,000,000)	(9,000,000)	(362,000,000)	(22,000,000)
Settlements, assets	(546,000,000)	(393,000,000)	(1,038,000,000)	(659,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	(616,000,000)	3,905,000,000	710,000,000	3,943,000,000
Bonds available for sale | Commercial mortgage-backed securities (CMBS)
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	596,000,000	99,000,000	722,000,000	241,000,000
Sales, assets	(69,000,000)	(20,000,000)	(133,000,000)	(20,000,000)
Settlements, assets	(35,000,000)	(79,000,000)	(86,000,000)	(149,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	492,000,000		503,000,000	72,000,000
Bonds available for sale | Collateralized Debt Obligations/Asset Backed Securities (CDO/ABS)
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	203,000,000	196,000,000	520,000,000	261,000,000
Sales, assets			(4,000,000)
Settlements, assets	(294,000,000)	(578,000,000)	(537,000,000)	(1,098,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	(91,000,000)	(382,000,000)	(21,000,000)	(837,000,000)
Bond trading securities
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	5,095,000,000	304,000,000	5,208,000,000	307,000,000
Sales, assets	(49,000,000)	(175,000,000)	(416,000,000)	(180,000,000)
Settlements, assets	(267,000,000)	(161,000,000)	(1,806,000,000)	(216,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	4,779,000,000	(32,000,000)	2,986,000,000	(89,000,000)
Bond trading securities | Corporate debt
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Settlements, assets	(2,000,000)	(9,000,000)	(4,000,000)	(9,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	(2,000,000)	(9,000,000)	(4,000,000)	(9,000,000)
Bond trading securities | Residential mortgage backed securities (RMBS)
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets		103,000,000		103,000,000
Settlements, assets	(19,000,000)	(23,000,000)	(38,000,000)	(17,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	(19,000,000)	80,000,000	(38,000,000)	86,000,000
Bond trading securities | Commercial mortgage-backed securities (CMBS)
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	70,000,000	60,000,000	183,000,000	60,000,000
Sales, assets	(49,000,000)	(49,000,000)	(106,000,000)	(54,000,000)
Settlements, assets	(8,000,000)	(29,000,000)	(199,000,000)	(82,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	13,000,000	(18,000,000)	(122,000,000)	(76,000,000)
Bond trading securities | Collateralized Debt Obligations/Asset Backed Securities (CDO/ABS)
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	5,025,000,000	141,000,000	5,025,000,000	144,000,000
Sales, assets		(126,000,000)	(310,000,000)	(126,000,000)
Settlements, assets	(238,000,000)	(100,000,000)	(1,565,000,000)	(108,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	4,787,000,000	(85,000,000)	3,150,000,000	(90,000,000)
Securities purchased through FRBNY's auction of Maiden Lane III assets	5,000,000,000		5,000,000,000
Fair value of additional securities purchase through additional auctions of Maiden Lane III assets	2,100,000,000		2,100,000,000
Equity securities
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	56,000,000		67,000,000
Sales, assets	(19,000,000)	(8,000,000)	(33,000,000)	(23,000,000)
Settlements, assets	5,000,000	(6,000,000)	2,000,000	(5,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	42,000,000	(14,000,000)	36,000,000	(28,000,000)
Other invested assets
Fair value assets and liabilities measured on recurring basis, unobservable input reconciliation
Purchases, assets	134,000,000	236,000,000	400,000,000	350,000,000
Sales, assets	(29,000,000)	(146,000,000)	(33,000,000)	(158,000,000)
Settlements, assets	(173,000,000)	(251,000,000)	(334,000,000)	(703,000,000)
Purchases, Sales, Issues and Settlements, Net, assets	$ (68,000,000)	$ (161,000,000)	$ 33,000,000	$ (511,000,000)