SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Variable Interest Entity
Total involvement with SPE assets	$ 617,454,000,000	$ 684,836,000,000
Consolidated VIE / SPE assets	117,089,000,000	131,599,000,000
Significant unconsolidated VIE assets	500,365,000,000	553,237,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	22,731,000,000	23,643,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,830,000,000	4,355,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	18,520,000,000	24,866,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	629,000,000	558,000,000
Maximum exposure to loss in significant unconsolidated VIEs	45,710,000,000	53,422,000,000
Citicorp
Variable Interest Entity
Total involvement with SPE assets	445,001,000,000	468,791,000,000
Consolidated VIE / SPE assets	106,824,000,000	120,653,000,000
Significant unconsolidated VIE assets	338,177,000,000	348,138,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	18,254,000,000	15,968,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,533,000,000	4,008,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	17,190,000,000	23,546,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	232,000,000	226,000,000
Maximum exposure to loss in significant unconsolidated VIEs	39,209,000,000	43,748,000,000
Citicorp | Mortgage-backed securities
Unfunded Exposure
Private label mortgage-backed securities, outstanding	19,000,000,000
Citicorp | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	75,694,000,000	87,083,000,000
Consolidated VIE / SPE assets	75,694,000,000	87,083,000,000
Citicorp | U.S. government-sponsored agency guaranteed
Variable Interest Entity
Total involvement with SPE assets	234,332,000,000	232,179,000,000
Significant unconsolidated VIE assets	234,332,000,000	232,179,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	2,606,000,000	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	2,629,000,000	3,795,000,000
Citicorp | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets	9,416,000,000	9,743,000,000
Consolidated VIE / SPE assets	1,320,000,000	1,622,000,000
Significant unconsolidated VIE assets	8,096,000,000	8,121,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	398,000,000	348,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	398,000,000	348,000,000
Citicorp | Citi-administered asset-backed commercial paper conduits (ABCP)
Variable Interest Entity
Total involvement with SPE assets	28,231,000,000	34,987,000,000
Consolidated VIE / SPE assets	20,325,000,000	21,971,000,000
Significant unconsolidated VIE assets	7,906,000,000	13,016,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	7,906,000,000	13,016,000,000
Maximum exposure to loss in significant unconsolidated VIEs	7,906,000,000	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	5,563,000,000	3,334,000,000
Significant unconsolidated VIE assets	5,563,000,000	3,334,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	25,000,000	20,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	25,000,000	20,000,000
Citicorp | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	10,565,000,000	8,127,000,000
Significant unconsolidated VIE assets	10,565,000,000	8,127,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	398,000,000	64,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	20,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	418,000,000	64,000,000
Citicorp | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	27,004,000,000	19,034,000,000
Consolidated VIE / SPE assets	1,163,000,000	1,303,000,000
Significant unconsolidated VIE assets	25,841,000,000	17,731,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	11,914,000,000	7,892,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	81,000,000	2,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	2,883,000,000	2,891,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	117,000,000	121,000,000
Maximum exposure to loss in significant unconsolidated VIEs	14,995,000,000	10,906,000,000
Citicorp | Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
Total involvement with SPE assets	15,512,000,000	16,849,000,000
Consolidated VIE / SPE assets	7,726,000,000	8,224,000,000
Significant unconsolidated VIE assets	7,786,000,000	8,625,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	304,000,000	708,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	4,785,000,000	5,413,000,000
Maximum exposure to loss in significant unconsolidated VIEs	5,089,000,000	6,121,000,000
Citicorp | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	19,030,000,000	20,331,000,000
Consolidated VIE / SPE assets	275,000,000	299,000,000
Significant unconsolidated VIE assets	18,755,000,000	20,032,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	1,949,000,000	2,345,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	2,998,000,000	3,535,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,454,000,000	1,586,000,000
Maximum exposure to loss in significant unconsolidated VIEs	6,401,000,000	7,466,000,000
Citicorp | Client intermediation
Variable Interest Entity
Total involvement with SPE assets	2,369,000,000	2,110,000,000
Consolidated VIE / SPE assets	170,000,000	24,000,000
Significant unconsolidated VIE assets	2,199,000,000	2,086,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	337,000,000	468,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	337,000,000	468,000,000
Citicorp | Investment funds
Variable Interest Entity
Total involvement with SPE assets	2,108,000,000	3,415,000,000
Consolidated VIE / SPE assets	21,000,000	30,000,000
Significant unconsolidated VIE assets	2,087,000,000	3,385,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	29,000,000	171,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		63,000,000
Maximum exposure to loss in significant unconsolidated VIEs	29,000,000	234,000,000
Citicorp | Trust preferred securities.
Variable Interest Entity
Total involvement with SPE assets	12,699,000,000	17,882,000,000
Significant unconsolidated VIE assets	12,699,000,000	17,882,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	127,000,000	128,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	127,000,000	128,000,000
Citicorp | Other
Variable Interest Entity
Total involvement with SPE assets	2,478,000,000	6,210,000,000
Consolidated VIE / SPE assets	130,000,000	97,000,000
Significant unconsolidated VIE assets	2,348,000,000	6,113,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	323,000,000	354,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	278,000,000	172,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	162,000,000	279,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	92,000,000	79,000,000
Maximum exposure to loss in significant unconsolidated VIEs	855,000,000	884,000,000
Citi Holdings
Variable Interest Entity
Total involvement with SPE assets	172,453,000,000	216,045,000,000
Consolidated VIE / SPE assets	10,265,000,000	10,946,000,000
Significant unconsolidated VIE assets	162,188,000,000	205,099,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	4,477,000,000	7,675,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	297,000,000	347,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,330,000,000	1,320,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	397,000,000	332,000,000
Maximum exposure to loss in significant unconsolidated VIEs	6,501,000,000	9,674,000,000
Citi Holdings | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	781,000,000	780,000,000
Consolidated VIE / SPE assets	399,000,000	581,000,000
Significant unconsolidated VIE assets	382,000,000	199,000,000
Citi Holdings | U.S. government-sponsored agency guaranteed
Variable Interest Entity
Total involvement with SPE assets	118,940,000,000	152,265,000,000
Significant unconsolidated VIE assets	118,940,000,000	152,265,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	695,000,000	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	838,000,000	1,279,000,000
Citi Holdings | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets	17,623,000,000	20,821,000,000
Consolidated VIE / SPE assets	1,670,000,000	1,764,000,000
Significant unconsolidated VIE assets	15,953,000,000	19,057,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	47,000,000	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	49,000,000	63,000,000
Citi Holdings | Student loan securitizations
Variable Interest Entity
Total involvement with SPE assets	1,723,000,000	1,822,000,000
Consolidated VIE / SPE assets	1,723,000,000	1,822,000,000
Citi Holdings | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets	5,028,000,000	6,581,000,000
Significant unconsolidated VIE assets	5,028,000,000	6,581,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	125,000,000	117,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	151,000,000	120,000,000
Maximum exposure to loss in significant unconsolidated VIEs	276,000,000	237,000,000
Citi Holdings | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	4,884,000,000	7,479,000,000
Significant unconsolidated VIE assets	4,884,000,000	7,479,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	438,000,000	1,125,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		6,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	101,000,000	90,000,000
Maximum exposure to loss in significant unconsolidated VIEs	539,000,000	1,221,000,000
Citi Holdings | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	7,945,000,000	10,490,000,000
Consolidated VIE / SPE assets	3,000,000	73,000,000
Significant unconsolidated VIE assets	7,942,000,000	10,417,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	3,048,000,000	5,004,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	11,000,000	3,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	328,000,000	250,000,000
Maximum exposure to loss in significant unconsolidated VIEs	3,387,000,000	5,257,000,000
Citi Holdings | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	7,758,000,000	7,820,000,000
Significant unconsolidated VIE assets	7,758,000,000	7,820,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	124,000,000	206,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	237,000,000	265,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,002,000,000	1,049,000,000
Maximum exposure to loss in significant unconsolidated VIEs	1,363,000,000	1,520,000,000
Citi Holdings | Client intermediation
Variable Interest Entity
Total involvement with SPE assets	33,000,000	111,000,000
Consolidated VIE / SPE assets	33,000,000	111,000,000
Citi Holdings | Investment funds
Variable Interest Entity
Total involvement with SPE assets	1,151,000,000	1,114,000,000
Consolidated VIE / SPE assets		14,000,000
Significant unconsolidated VIE assets	1,151,000,000	1,100,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	46,000,000	43,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	46,000,000	43,000,000
Citi Holdings | Other
Variable Interest Entity
Total involvement with SPE assets	6,587,000,000	6,762,000,000
Consolidated VIE / SPE assets	6,437,000,000	6,581,000,000
Significant unconsolidated VIE assets	150,000,000	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	3,000,000	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	$ 3,000,000	$ 54,000,000