SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Schedule of Variable Interest Entities (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Variable Interest Entity
Total involvement with SPE assets	$ 517,881,000,000	$ 536,710,000,000
Consolidated VIE / SPE assets	98,544,000,000	102,790,000,000
Significant unconsolidated VIE assets	419,337,000,000	433,920,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	30,073,000,000	32,909,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,488,000,000	4,102,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	9,078,000,000	8,313,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	590,000,000	613,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	43,229,000,000	45,937,000,000
Citicorp
Variable Interest Entity
Total involvement with SPE assets	469,420,000,000	483,934,000,000
Consolidated VIE / SPE assets	94,222,000,000	100,050,000,000
Significant unconsolidated VIE assets	375,198,000,000	383,884,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	29,711,000,000	32,475,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	3,317,000,000	3,923,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	8,109,000,000	7,323,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	416,000,000	435,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	41,553,000,000	44,156,000,000
Citicorp | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	55,367,000,000	60,211,000,000
Consolidated VIE / SPE assets	55,367,000,000	60,211,000,000
Significant unconsolidated VIE assets	0	0
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	0	0
Citicorp | Mortgage-backed securities - U.S. agency-sponsored
Variable Interest Entity
Total involvement with SPE assets	230,798,000,000	236,771,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	230,798,000,000	236,771,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	3,000,000,000	5,063,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	18,000,000	19,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	3,018,000,000	5,082,000,000
Citicorp | Mortgage securitizations - Non-agency-sponsored
Variable Interest Entity
Total involvement with SPE assets	7,457,000,000	8,071,000,000
Consolidated VIE / SPE assets	1,018,000,000	1,239,000,000
Significant unconsolidated VIE assets	6,439,000,000	6,832,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	530,000,000	560,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	530,000,000	560,000,000
Citicorp | Citi-administered asset-backed commercial paper conduits (ABCP)
Variable Interest Entity
Total involvement with SPE assets	28,807,000,000	29,181,000,000
Consolidated VIE / SPE assets	28,807,000,000	29,181,000,000
Significant unconsolidated VIE assets	0	0
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	0	0
Citicorp | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets	3,027,000,000	3,382,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	3,027,000,000	3,382,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	38,000,000	45,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	38,000,000	45,000,000
Citicorp | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	14,782,000,000	13,099,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	14,782,000,000	13,099,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	1,917,000,000	1,692,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	1,917,000,000	1,692,000,000
Citicorp | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	60,391,000,000	62,577,000,000
Consolidated VIE / SPE assets	1,102,000,000	1,149,000,000
Significant unconsolidated VIE assets	59,289,000,000	61,428,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	22,052,000,000	22,891,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	61,000,000	63,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	3,138,000,000	2,185,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	318,000,000	333,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	25,569,000,000	25,472,000,000
Citicorp | Municipal securities tender option bond trusts (TOBs)
Variable Interest Entity
Total involvement with SPE assets	12,017,000,000	12,280,000,000
Consolidated VIE / SPE assets	6,431,000,000	6,671,000,000
Significant unconsolidated VIE assets	5,586,000,000	5,609,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	0	3,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	3,645,000,000	3,670,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	3,645,000,000	3,673,000,000
Citicorp | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	16,736,000,000	16,825,000,000
Consolidated VIE / SPE assets	55,000,000	70,000,000
Significant unconsolidated VIE assets	16,681,000,000	16,755,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	2,035,000,000	2,012,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	1,833,000,000	2,021,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	1,162,000,000	1,321,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	5,030,000,000	5,354,000,000
Citicorp | Client intermediation
Variable Interest Entity
Total involvement with SPE assets	1,810,000,000	1,745,000,000
Consolidated VIE / SPE assets	105,000,000	137,000,000
Significant unconsolidated VIE assets	1,705,000,000	1,608,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	42,000,000	10,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	10,000,000	10,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	52,000,000	20,000,000
Citicorp | Investment funds
Variable Interest Entity
Total involvement with SPE assets	30,883,000,000	31,474,000,000
Consolidated VIE / SPE assets	1,049,000,000	1,096,000,000
Significant unconsolidated VIE assets	29,834,000,000	30,378,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	17,000,000	16,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	379,000,000	382,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	125,000,000	124,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	521,000,000	522,000,000
Citicorp | Trust preferred securities
Variable Interest Entity
Total involvement with SPE assets	2,632,000,000	2,633,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	2,632,000,000	2,633,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	6,000,000	6,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	6,000,000	6,000,000
Citicorp | Other
Variable Interest Entity
Total involvement with SPE assets	4,713,000,000	5,685,000,000
Consolidated VIE / SPE assets	288,000,000	296,000,000
Significant unconsolidated VIE assets	4,425,000,000	5,389,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	80,000,000	183,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	1,038,000,000	1,451,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	39,000,000	23,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	70,000,000	73,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	1,227,000,000	1,730,000,000
Citicorp | Mortgage-backed securities
Funded and Unfunded Exposure
Private label mortgage-backed securities, outstanding	14,000,000,000	14,000,000,000
Citi Holdings
Variable Interest Entity
Total involvement with SPE assets	48,461,000,000	52,776,000,000
Consolidated VIE / SPE assets	4,322,000,000	2,740,000,000
Significant unconsolidated VIE assets	44,139,000,000	50,036,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	362,000,000	434,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	171,000,000	179,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	969,000,000	990,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	174,000,000	178,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	1,676,000,000	1,781,000,000
Citi Holdings | Credit card securitizations
Variable Interest Entity
Total involvement with SPE assets	254,000,000	292,000,000
Consolidated VIE / SPE assets	54,000,000	60,000,000
Significant unconsolidated VIE assets	200,000,000	232,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	0	0
Citi Holdings | Mortgage-backed securities - U.S. agency-sponsored
Variable Interest Entity
Total involvement with SPE assets	23,286,000,000	28,077,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	23,286,000,000	28,077,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	110,000,000	150,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	88,000,000	91,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	198,000,000	241,000,000
Citi Holdings | Mortgage securitizations - Non-agency-sponsored
Variable Interest Entity
Total involvement with SPE assets	9,246,000,000	9,817,000,000
Consolidated VIE / SPE assets	63,000,000	65,000,000
Significant unconsolidated VIE assets	9,183,000,000	9,752,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	18,000,000	17,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	1,000,000	1,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	19,000,000	18,000,000
Citi Holdings | Collateralized debt obligations (CDOs)
Variable Interest Entity
Total involvement with SPE assets	2,126,000,000	2,235,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	2,126,000,000	2,235,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	156,000,000	174,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	85,000,000	86,000,000
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	241,000,000	260,000,000
Citi Holdings | Collateralized loan obligations (CLOs)
Variable Interest Entity
Total involvement with SPE assets	834,000,000	1,020,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	834,000,000	1,020,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	37,000,000	54,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	37,000,000	54,000,000
Citi Holdings | Asset-based financing
Variable Interest Entity
Total involvement with SPE assets	1,167,000,000	1,323,000,000
Consolidated VIE / SPE assets	2,000,000	2,000,000
Significant unconsolidated VIE assets	1,165,000,000	1,321,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	39,000,000	37,000,000
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	81,000,000	86,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	123,000,000	126,000,000
Citi Holdings | Municipal investments
Variable Interest Entity
Total involvement with SPE assets	6,838,000,000	6,881,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	6,838,000,000	6,881,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	2,000,000	2,000,000
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	168,000,000	176,000,000
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	888,000,000	904,000,000
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	1,058,000,000	1,082,000,000
Citi Holdings | Investment funds
Variable Interest Entity
Total involvement with SPE assets	507,000,000	518,000,000
Consolidated VIE / SPE assets	0	0
Significant unconsolidated VIE assets	507,000,000	518,000,000
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	0	0
Citi Holdings | Other
Variable Interest Entity
Total involvement with SPE assets	4,203,000,000	2,613,000,000
Consolidated VIE / SPE assets	4,203,000,000	2,613,000,000
Significant unconsolidated VIE assets	0	0
Funded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, debt investments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, equity investments	0	0
Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs, funding commitments	0	0
Maximum exposure to loss in significant unconsolidated VIEs, guarantees and derivatives	0	0
Funded and Unfunded Exposure
Maximum exposure to loss in significant unconsolidated VIEs	$ 0	$ 0