SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Variable Interest Entity
Total involvement with SPE assets		$ 548,837,000,000	$ 623,652,000,000
Consolidated VIE / SPE assets		97,270,000,000	124,171,000,000
Significant unconsolidated VIE assets		451,567,000,000	499,481,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		24,638,000,000	24,066,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		3,800,000,000	3,965,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		10,109,000,000	17,263,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		628,000,000	677,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		39,175,000,000	45,971,000,000
Citicorp
Variable Interest Entity
Total involvement with SPE assets		419,551,000,000	467,253,000,000
Consolidated VIE / SPE assets		87,320,000,000	112,760,000,000
Significant unconsolidated VIE assets		332,231,000,000	354,493,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		22,725,000,000	21,675,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		3,510,000,000	3,674,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		8,909,000,000	16,015,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		269,000,000	280,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		35,413,000,000	41,644,000,000
Citicorp | Mortgage-backed securities
Funded and Unfunded Exposure
Private label mortgage-backed securities, outstanding		17,000,000,000	19,000,000,000
Citicorp | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets		44,893,000,000	77,770,000,000
Consolidated VIE / SPE assets		44,893,000,000	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		233,282,000,000	232,741,000,000
Significant unconsolidated VIE assets		233,282,000,000	232,741,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		3,490,000,000	3,042,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		41,000,000	45,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		3,531,000,000	3,087,000,000
Citicorp | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets		7,828,000,000	8,810,000,000
Consolidated VIE / SPE assets		914,000,000	1,188,000,000
Significant unconsolidated VIE assets		6,914,000,000	7,622,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		517,000,000	382,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		517,000,000	382,000,000
Citicorp | Citi-administered asset-backed commercial paper conduits (ABCP)
Variable Interest Entity
Total involvement with SPE assets		28,705,000,000	30,002,000,000
Consolidated VIE / SPE assets		28,705,000,000	22,387,000,000
Significant unconsolidated VIE assets			7,615,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments			7,615,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs			7,615,000,000
Citicorp | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets		4,502,000,000	5,539,000,000
Significant unconsolidated VIE assets		4,502,000,000	5,539,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		50,000,000	24,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		50,000,000	24,000,000
Citicorp | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets		11,426,000,000	15,120,000,000
Significant unconsolidated VIE assets		11,426,000,000	15,120,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		1,298,000,000	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		1,298,000,000	661,000,000
Citicorp | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets		38,584,000,000	41,399,000,000
Consolidated VIE / SPE assets		1,012,000,000	1,125,000,000
Significant unconsolidated VIE assets		37,572,000,000	40,274,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		14,985,000,000	14,798,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		73,000,000	84,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		2,941,000,000	2,081,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		157,000,000	159,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		18,156,000,000	17,122,000,000
Citicorp | Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
Total involvement with SPE assets		13,798,000,000	15,163,000,000
Consolidated VIE / SPE assets		7,205,000,000	7,573,000,000
Significant unconsolidated VIE assets		6,593,000,000	7,590,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		84,000,000	352,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		4,398,000,000	4,628,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		4,482,000,000	4,980,000,000
Citicorp | Municipal investments
Variable Interest Entity
Total involvement with SPE assets		18,085,000,000	19,693,000,000
Consolidated VIE / SPE assets		229,000,000	255,000,000
Significant unconsolidated VIE assets		17,856,000,000	19,438,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		1,939,000,000	2,003,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		2,797,000,000	3,049,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		1,522,000,000	1,669,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		6,258,000,000	6,721,000,000
Citicorp | Client intermediation
Variable Interest Entity
Total involvement with SPE assets		2,047,000,000	2,486,000,000
Consolidated VIE / SPE assets		65,000,000	151,000,000
Significant unconsolidated VIE assets		1,982,000,000	2,335,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		243,000,000	319,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		243,000,000	319,000,000
Citicorp | Investment funds
Variable Interest Entity
Total involvement with SPE assets		5,819,000,000	4,286,000,000
Consolidated VIE / SPE assets		4,004,000,000	2,196,000,000
Significant unconsolidated VIE assets		1,815,000,000	2,090,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		49,000,000	14,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		49,000,000	14,000,000
Citicorp | Trust preferred securities
Variable Interest Entity
Total involvement with SPE assets		8,420,000,000	12,221,000,000
Significant unconsolidated VIE assets		8,420,000,000	12,221,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		63,000,000	126,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		63,000,000	126,000,000
Citicorp | Other
Variable Interest Entity
Total involvement with SPE assets		2,162,000,000	2,023,000,000
Consolidated VIE / SPE assets		293,000,000	115,000,000
Significant unconsolidated VIE assets		1,869,000,000	1,908,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		119,000,000	113,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		528,000,000	382,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		48,000,000	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		766,000,000	593,000,000
Citi Holdings
Variable Interest Entity
Total involvement with SPE assets		129,286,000,000	156,399,000,000
Consolidated VIE / SPE assets		9,950,000,000	11,411,000,000
Significant unconsolidated VIE assets		119,336,000,000	144,988,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		1,913,000,000	2,391,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		290,000,000	291,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		1,200,000,000	1,248,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		359,000,000	397,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		3,762,000,000	4,327,000,000
Citi Holdings | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets		1,809,000,000	2,177,000,000
Consolidated VIE / SPE assets		1,485,000,000	1,736,000,000
Significant unconsolidated VIE assets		324,000,000	441,000,000
Citi Holdings | U.S. government-sponsored agency guaranteed
Variable Interest Entity
Total involvement with SPE assets		85,833,000,000	106,888,000,000
Significant unconsolidated VIE assets		85,833,000,000	106,888,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		699,000,000	700,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		142,000,000	163,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		841,000,000	863,000,000
Citi Holdings | Non-agency-sponsored mortgages
Variable Interest Entity
Total involvement with SPE assets		15,251,000,000	17,192,000,000
Consolidated VIE / SPE assets		1,893,000,000	2,127,000,000
Significant unconsolidated VIE assets		13,358,000,000	15,065,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		48,000,000	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		50,000,000	45,000,000
Citi Holdings | Student loan securitizations
Variable Interest Entity
Total involvement with SPE assets		1,602,000,000	1,681,000,000
Consolidated VIE / SPE assets		1,602,000,000	1,681,000,000
Citi Holdings | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets		4,191,000,000	4,752,000,000
Significant unconsolidated VIE assets		4,191,000,000	4,752,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		138,000,000	139,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		105,000,000	124,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		243,000,000	263,000,000
Citi Holdings | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets		3,215,000,000	4,676,000,000
Significant unconsolidated VIE assets		3,215,000,000	4,676,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		388,000,000	435,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		8,000,000	13,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives		110,000,000	108,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		506,000,000	556,000,000
Citi Holdings | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets		3,442,000,000	4,166,000,000
Consolidated VIE / SPE assets		3,000,000	3,000,000
Significant unconsolidated VIE assets		3,439,000,000	4,163,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		621,000,000	984,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		3,000,000	6,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		240,000,000	243,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		864,000,000	1,233,000,000
Citi Holdings | Municipal investments
Variable Interest Entity
Total involvement with SPE assets		7,492,000,000	7,766,000,000
Significant unconsolidated VIE assets		7,492,000,000	7,766,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments		19,000,000	90,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		226,000,000	235,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments		952,000,000	992,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		1,197,000,000	1,317,000,000
Citi Holdings | Client intermediation
Variable Interest Entity
Total involvement with SPE assets		10,000,000	13,000,000
Consolidated VIE / SPE assets		10,000,000	13,000,000
Citi Holdings | Investment funds
Variable Interest Entity
Total involvement with SPE assets		1,362,000,000	1,083,000,000
Significant unconsolidated VIE assets		1,362,000,000	1,083,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments		61,000,000	47,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs		61,000,000	47,000,000
Citi Holdings | Other
Variable Interest Entity
Total involvement with SPE assets		5,079,000,000	6,005,000,000
Consolidated VIE / SPE assets		4,957,000,000	5,851,000,000
Significant unconsolidated VIE assets		122,000,000	154,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, equity investments			3,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs			$ 3,000,000