SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Variable Interest Entity
Total involvement with SPE assets	$ 632,581,000,000	$ 684,836,000,000
Consolidated VIE / SPE assets	119,443,000,000	131,599,000,000
Significant unconsolidated VIE assets	513,138,000,000	553,237,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	23,358,000,000	23,643,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	4,455,000,000	4,355,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	19,306,000,000	24,866,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	607,000,000	558,000,000
Maximum exposure to loss in significant unconsolidated VIEs	47,726,000,000	53,422,000,000
Citicorp
Variable Interest Entity
Total involvement with SPE assets	448,373,000,000	468,791,000,000
Consolidated VIE / SPE assets	108,891,000,000	120,653,000,000
Significant unconsolidated VIE assets	339,482,000,000	348,138,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	18,468,000,000	15,968,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	4,160,000,000	4,008,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	17,989,000,000	23,546,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	242,000,000	226,000,000
Maximum exposure to loss in significant unconsolidated VIEs	40,859,000,000	43,748,000,000
Citicorp | Mortgage-backed securities
Unfunded Exposure
Private label mortgage-backed securities, outstanding	20,000,000,000
Citicorp | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	76,716,000,000	87,083,000,000
Consolidated VIE / SPE assets	76,716,000,000	87,083,000,000
Citicorp | U.S. government-sponsored agency guaranteed
Variable Interest Entity
Total involvement with SPE assets	239,887,000,000	232,179,000,000
Significant unconsolidated VIE assets	239,887,000,000	232,179,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	3,707,000,000	3,769,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	23,000,000	26,000,000
Maximum exposure to loss in significant unconsolidated VIEs	3,730,000,000	3,795,000,000
Citicorp | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets	9,485,000,000	9,743,000,000
Consolidated VIE / SPE assets	1,425,000,000	1,622,000,000
Significant unconsolidated VIE assets	8,060,000,000	8,121,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	400,000,000	348,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	400,000,000	348,000,000
Citicorp | Citi-administered asset-backed commercial paper conduits (ABCP)
Variable Interest Entity
Total involvement with SPE assets	29,724,000,000	34,987,000,000
Consolidated VIE / SPE assets	21,093,000,000	21,971,000,000
Significant unconsolidated VIE assets	8,631,000,000	13,016,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	8,631,000,000	13,016,000,000
Maximum exposure to loss in significant unconsolidated VIEs	8,631,000,000	13,016,000,000
Citicorp | Third-party commercial paper conduits
Variable Interest Entity
Total involvement with SPE assets		7,507,000,000
Significant unconsolidated VIE assets		7,507,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		298,000,000
Maximum exposure to loss in significant unconsolidated VIEs		298,000,000
Citicorp | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets	2,730,000,000	3,334,000,000
Significant unconsolidated VIE assets	2,730,000,000	3,334,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	9,000,000	20,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	9,000,000	20,000,000
Citicorp | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	7,387,000,000	8,127,000,000
Significant unconsolidated VIE assets	7,387,000,000	8,127,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	508,000,000	64,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	22,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	530,000,000	64,000,000
Citicorp | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	20,962,000,000	19,034,000,000
Consolidated VIE / SPE assets	1,180,000,000	1,303,000,000
Significant unconsolidated VIE assets	19,782,000,000	17,731,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	10,339,000,000	7,892,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	31,000,000	2,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	2,739,000,000	2,891,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	130,000,000	121,000,000
Maximum exposure to loss in significant unconsolidated VIEs	13,239,000,000	10,906,000,000
Citicorp | Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
Total involvement with SPE assets	16,101,000,000	16,849,000,000
Consolidated VIE / SPE assets	8,004,000,000	8,224,000,000
Significant unconsolidated VIE assets	8,097,000,000	8,625,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	707,000,000	708,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	4,817,000,000	5,413,000,000
Maximum exposure to loss in significant unconsolidated VIEs	5,524,000,000	6,121,000,000
Citicorp | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	20,182,000,000	20,331,000,000
Consolidated VIE / SPE assets	291,000,000	299,000,000
Significant unconsolidated VIE assets	19,891,000,000	20,032,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	2,198,000,000	2,345,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,549,000,000	3,535,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,470,000,000	1,586,000,000
Maximum exposure to loss in significant unconsolidated VIEs	7,217,000,000	7,466,000,000
Citicorp | Client intermediation
Variable Interest Entity
Total involvement with SPE assets	1,762,000,000	2,110,000,000
Consolidated VIE / SPE assets	32,000,000	24,000,000
Significant unconsolidated VIE assets	1,730,000,000	2,086,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	334,000,000	468,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	334,000,000	468,000,000
Citicorp | Investment funds
Variable Interest Entity
Total involvement with SPE assets	3,215,000,000	3,415,000,000
Consolidated VIE / SPE assets	24,000,000	30,000,000
Significant unconsolidated VIE assets	3,191,000,000	3,385,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	141,000,000	171,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	43,000,000	63,000,000
Maximum exposure to loss in significant unconsolidated VIEs	184,000,000	234,000,000
Citicorp | Trust preferred securities.
Variable Interest Entity
Total involvement with SPE assets	17,960,000,000	17,882,000,000
Significant unconsolidated VIE assets	17,960,000,000	17,882,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	128,000,000	128,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	128,000,000	128,000,000
Citicorp | Other
Variable Interest Entity
Total involvement with SPE assets	2,262,000,000	6,210,000,000
Consolidated VIE / SPE assets	126,000,000	97,000,000
Significant unconsolidated VIE assets	2,136,000,000	6,113,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	266,000,000	354,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	289,000,000	172,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	289,000,000	279,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	89,000,000	79,000,000
Maximum exposure to loss in significant unconsolidated VIEs	933,000,000	884,000,000
Citi Holdings
Variable Interest Entity
Total involvement with SPE assets	184,208,000,000	216,045,000,000
Consolidated VIE / SPE assets	10,552,000,000	10,946,000,000
Significant unconsolidated VIE assets	173,656,000,000	205,099,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	4,890,000,000	7,675,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	295,000,000	347,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,317,000,000	1,320,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	365,000,000	332,000,000
Maximum exposure to loss in significant unconsolidated VIEs	6,867,000,000	9,674,000,000
Citi Holdings | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	579,000,000	780,000,000
Consolidated VIE / SPE assets	436,000,000	581,000,000
Significant unconsolidated VIE assets	143,000,000	199,000,000
Citi Holdings | U.S. government-sponsored agency guaranteed
Variable Interest Entity
Total involvement with SPE assets	129,908,000,000	152,265,000,000
Significant unconsolidated VIE assets	129,908,000,000	152,265,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	785,000,000	1,159,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	143,000,000	120,000,000
Maximum exposure to loss in significant unconsolidated VIEs	928,000,000	1,279,000,000
Citi Holdings | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets	18,493,000,000	20,821,000,000
Consolidated VIE / SPE assets	1,664,000,000	1,764,000,000
Significant unconsolidated VIE assets	16,829,000,000	19,057,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	51,000,000	61,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	2,000,000	2,000,000
Maximum exposure to loss in significant unconsolidated VIEs	53,000,000	63,000,000
Citi Holdings | Student loan securitizations
Variable Interest Entity
Total involvement with SPE assets	1,752,000,000	1,822,000,000
Consolidated VIE / SPE assets	1,752,000,000	1,822,000,000
Citi Holdings | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets	5,397,000,000	6,581,000,000
Significant unconsolidated VIE assets	5,397,000,000	6,581,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	142,000,000	117,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	123,000,000	120,000,000
Maximum exposure to loss in significant unconsolidated VIEs	265,000,000	237,000,000
Citi Holdings | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	4,959,000,000	7,479,000,000
Significant unconsolidated VIE assets	4,959,000,000	7,479,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	435,000,000	1,125,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	6,000,000	6,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	97,000,000	90,000,000
Maximum exposure to loss in significant unconsolidated VIEs	538,000,000	1,221,000,000
Citi Holdings | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	7,432,000,000	10,490,000,000
Consolidated VIE / SPE assets	3,000,000	73,000,000
Significant unconsolidated VIE assets	7,429,000,000	10,417,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	3,328,000,000	5,004,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,000,000	3,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	279,000,000	250,000,000
Maximum exposure to loss in significant unconsolidated VIEs	3,610,000,000	5,257,000,000
Citi Holdings | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	7,722,000,000	7,820,000,000
Significant unconsolidated VIE assets	7,722,000,000	7,820,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	149,000,000	206,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	238,000,000	265,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,032,000,000	1,049,000,000
Maximum exposure to loss in significant unconsolidated VIEs	1,419,000,000	1,520,000,000
Citi Holdings | Client intermediation
Variable Interest Entity
Total involvement with SPE assets	35,000,000	111,000,000
Consolidated VIE / SPE assets	35,000,000	111,000,000
Citi Holdings | Investment funds
Variable Interest Entity
Total involvement with SPE assets	1,123,000,000	1,114,000,000
Consolidated VIE / SPE assets	14,000,000	14,000,000
Significant unconsolidated VIE assets	1,109,000,000	1,100,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	45,000,000	43,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	45,000,000	43,000,000
Citi Holdings | Other
Variable Interest Entity
Total involvement with SPE assets	6,808,000,000	6,762,000,000
Consolidated VIE / SPE assets	6,648,000,000	6,581,000,000
Significant unconsolidated VIE assets	160,000,000	181,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		3,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	9,000,000	36,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		15,000,000
Maximum exposure to loss in significant unconsolidated VIEs	$ 9,000,000	$ 54,000,000