SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Variable Interest Entity
Total involvement with SPE assets	$ 570,947,000,000	$ 623,652,000,000
Consolidated VIE / SPE assets	93,773,000,000	124,171,000,000
Significant unconsolidated VIE assets	477,174,000,000	499,481,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	24,117,000,000	24,066,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,949,000,000	3,965,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	16,407,000,000	17,263,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	655,000,000	677,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	45,128,000,000	45,971,000,000
Citicorp
Variable Interest Entity
Total involvement with SPE assets	428,134,000,000	467,253,000,000
Consolidated VIE / SPE assets	83,040,000,000	112,760,000,000
Significant unconsolidated VIE assets	345,094,000,000	354,493,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	21,954,000,000	21,675,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,653,000,000	3,674,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	15,189,000,000	16,015,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	267,000,000	280,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	41,063,000,000	41,644,000,000
Citicorp | Mortgage-backed securities
Funded and Unfunded Exposure
Private label mortgage-backed securities, outstanding	18,000,000,000
Citicorp | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	45,983,000,000	77,770,000,000
Consolidated VIE / SPE assets	45,983,000,000	77,770,000,000
Funded and Unfunded Exposure
Amount removed from receivables	27,000,000,000
Citicorp | Credit card securitizations | Citibank Credit Card Master Trust (Master Trust)
Funded and Unfunded Exposure
Amount removed from receivables	12,000,000,000
Citicorp | Credit card securitizations | Citibank OMNI Master Trust (Omni Trust)
Funded and Unfunded Exposure
Amount removed from receivables	15,000,000,000
Citicorp | U.S. government-sponsored agency guaranteed
Variable Interest Entity
Total involvement with SPE assets	232,908,000,000	232,741,000,000
Significant unconsolidated VIE assets	232,908,000,000	232,741,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	3,494,000,000	3,042,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	43,000,000	45,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	3,537,000,000	3,087,000,000
Citicorp | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets	8,796,000,000	8,810,000,000
Consolidated VIE / SPE assets	1,098,000,000	1,188,000,000
Significant unconsolidated VIE assets	7,698,000,000	7,622,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	522,000,000	382,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	522,000,000	382,000,000
Citicorp | Citi-administered asset-backed commercial paper conduits (ABCP)
Variable Interest Entity
Total involvement with SPE assets	29,114,000,000	30,002,000,000
Consolidated VIE / SPE assets	21,851,000,000	22,387,000,000
Significant unconsolidated VIE assets	7,263,000,000	7,615,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	7,263,000,000	7,615,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	7,263,000,000	7,615,000,000
Citicorp | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets	4,663,000,000	5,539,000,000
Significant unconsolidated VIE assets	4,663,000,000	5,539,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	25,000,000	24,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	25,000,000	24,000,000
Citicorp | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	11,790,000,000	15,120,000,000
Significant unconsolidated VIE assets	11,790,000,000	15,120,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	347,000,000	642,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		19,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	347,000,000	661,000,000
Citicorp | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	38,029,000,000	41,399,000,000
Consolidated VIE / SPE assets	1,019,000,000	1,125,000,000
Significant unconsolidated VIE assets	37,010,000,000	40,274,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	15,181,000,000	14,798,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	78,000,000	84,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,649,000,000	2,081,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	153,000,000	159,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	17,061,000,000	17,122,000,000
Citicorp | Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
Total involvement with SPE assets	14,666,000,000	15,163,000,000
Consolidated VIE / SPE assets	7,491,000,000	7,573,000,000
Significant unconsolidated VIE assets	7,175,000,000	7,590,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	47,000,000	352,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	4,591,000,000	4,628,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	4,638,000,000	4,980,000,000
Citicorp | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	19,319,000,000	19,693,000,000
Consolidated VIE / SPE assets	236,000,000	255,000,000
Significant unconsolidated VIE assets	19,083,000,000	19,438,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	1,883,000,000	2,003,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,013,000,000	3,049,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,661,000,000	1,669,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	6,557,000,000	6,721,000,000
Citicorp | Client intermediation
Variable Interest Entity
Total involvement with SPE assets	2,356,000,000	2,486,000,000
Consolidated VIE / SPE assets	156,000,000	151,000,000
Significant unconsolidated VIE assets	2,200,000,000	2,335,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	319,000,000	319,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	319,000,000	319,000,000
Citicorp | Investment funds
Variable Interest Entity
Total involvement with SPE assets	7,032,000,000	4,286,000,000
Consolidated VIE / SPE assets	5,098,000,000	2,196,000,000
Significant unconsolidated VIE assets	1,934,000,000	2,090,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	43,000,000	14,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	43,000,000	14,000,000
Citicorp | Trust preferred securities
Variable Interest Entity
Total involvement with SPE assets	11,433,000,000	12,221,000,000
Significant unconsolidated VIE assets	11,433,000,000	12,221,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	126,000,000	126,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	126,000,000	126,000,000
Citicorp | Other
Variable Interest Entity
Total involvement with SPE assets	2,045,000,000	2,023,000,000
Consolidated VIE / SPE assets	108,000,000	115,000,000
Significant unconsolidated VIE assets	1,937,000,000	1,908,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	136,000,000	113,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	393,000,000	382,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	25,000,000	22,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	71,000,000	76,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	625,000,000	593,000,000
Citi Holdings
Variable Interest Entity
Total involvement with SPE assets	142,813,000,000	156,399,000,000
Consolidated VIE / SPE assets	10,733,000,000	11,411,000,000
Significant unconsolidated VIE assets	132,080,000,000	144,988,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	2,163,000,000	2,391,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	296,000,000	291,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,218,000,000	1,248,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	388,000,000	397,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	4,065,000,000	4,327,000,000
Citi Holdings | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	1,846,000,000	2,177,000,000
Consolidated VIE / SPE assets	1,467,000,000	1,736,000,000
Significant unconsolidated VIE assets	379,000,000	441,000,000
Citi Holdings | U.S. government-sponsored agency guaranteed
Variable Interest Entity
Total involvement with SPE assets	96,245,000,000	106,888,000,000
Significant unconsolidated VIE assets	96,245,000,000	106,888,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	702,000,000	700,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	150,000,000	163,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	852,000,000	863,000,000
Citi Holdings | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets	16,317,000,000	17,192,000,000
Consolidated VIE / SPE assets	2,069,000,000	2,127,000,000
Significant unconsolidated VIE assets	14,248,000,000	15,065,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	49,000,000	43,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	2,000,000	2,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	51,000,000	45,000,000
Citi Holdings | Student loan securitizations
Variable Interest Entity
Total involvement with SPE assets	1,642,000,000	1,681,000,000
Consolidated VIE / SPE assets	1,642,000,000	1,681,000,000
Citi Holdings | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets	4,494,000,000	4,752,000,000
Significant unconsolidated VIE assets	4,494,000,000	4,752,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	139,000,000	139,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	125,000,000	124,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	264,000,000	263,000,000
Citi Holdings | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	3,963,000,000	4,676,000,000
Significant unconsolidated VIE assets	3,963,000,000	4,676,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	384,000,000	435,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	16,000,000	13,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	111,000,000	108,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	511,000,000	556,000,000
Citi Holdings | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	3,784,000,000	4,166,000,000
Consolidated VIE / SPE assets	3,000,000	3,000,000
Significant unconsolidated VIE assets	3,781,000,000	4,163,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	853,000,000	984,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	5,000,000	6,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	237,000,000	243,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	1,095,000,000	1,233,000,000
Citi Holdings | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	7,528,000,000	7,766,000,000
Significant unconsolidated VIE assets	7,528,000,000	7,766,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	36,000,000	90,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	228,000,000	235,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	965,000,000	992,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	1,229,000,000	1,317,000,000
Citi Holdings | Client intermediation
Variable Interest Entity
Total involvement with SPE assets	11,000,000	13,000,000
Consolidated VIE / SPE assets	11,000,000	13,000,000
Citi Holdings | Investment funds
Variable Interest Entity
Total involvement with SPE assets	1,313,000,000	1,083,000,000
Significant unconsolidated VIE assets	1,313,000,000	1,083,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	60,000,000	47,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	60,000,000	47,000,000
Citi Holdings | Other
Variable Interest Entity
Total involvement with SPE assets	5,670,000,000	6,005,000,000
Consolidated VIE / SPE assets	5,541,000,000	5,851,000,000
Significant unconsolidated VIE assets	129,000,000	154,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,000,000	3,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	$ 3,000,000	$ 3,000,000