INVESTMENTS (Details 4) (USD $)	3 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Schedule of Held-to-maturity Securities
Fair value of AFS securities transferred to HTM	$ 11,800,000,000
Debt Securities Held-to-maturity
Amortized cost	23,322,000,000	[1]	11,274,000,000	[1]
Net unrealized losses recognized in AOCI	(992,000,000)		(675,000,000)
Carrying value	22,330,000,000	[2]	10,599,000,000	[2]
Gross unrecognized gains	1,206,000,000		769,000,000
Gross unrecognized losses	(509,000,000)		(375,000,000)
Fair value	23,027,000,000		10,993,000,000
Mortgage-backed securities - U.S. government-sponsored agency guaranteed
Schedule of Held-to-maturity Securities
Fair value of AFS securities transferred to HTM	5,400,000,000
Debt Securities Held-to-maturity
Amortized cost	5,316,000,000	[1],[3]
Net unrealized losses recognized in AOCI	97,000,000	[3]
Carrying value	5,413,000,000	[2],[3]
Gross unrecognized gains	12,000,000	[3]
Gross unrecognized losses	(11,000,000)	[3]
Fair value	5,414,000,000	[3]
Mortgage-backed securities - Prime
Debt Securities Held-to-maturity
Amortized cost	63,000,000	[1],[3]	72,000,000	[1],[3]
Net unrealized losses recognized in AOCI	(13,000,000)	[3]	(16,000,000)	[3]
Carrying value	50,000,000	[2],[3]	56,000,000	[2],[3]
Gross unrecognized gains	6,000,000	[3]	5,000,000	[3]
Gross unrecognized losses	(2,000,000)	[3]	(2,000,000)	[3]
Fair value	54,000,000	[3]	59,000,000	[3]
Mortgage-backed securities - Alt-A
Debt Securities Held-to-maturity
Amortized cost	1,261,000,000	[1],[3]	1,379,000,000	[1],[3]
Net unrealized losses recognized in AOCI	(256,000,000)	[3]	(287,000,000)	[3]
Carrying value	1,005,000,000	[2],[3]	1,092,000,000	[2],[3]
Gross unrecognized gains	519,000,000	[3]	449,000,000	[3]
Gross unrecognized losses	(266,000,000)	[3]	(263,000,000)	[3]
Fair value	1,258,000,000	[3]	1,278,000,000	[3]
Mortgage-backed securities - Subprime
Debt Securities Held-to-maturity
Amortized cost	2,000,000	[1],[3]	2,000,000	[1],[3]
Carrying value	2,000,000	[2],[3]	2,000,000	[2],[3]
Gross unrecognized gains	1,000,000	[3]	1,000,000	[3]
Fair value	3,000,000	[3]	3,000,000	[3]
Mortgage-backed securities - Non-U.S. residential
Debt Securities Held-to-maturity
Amortized cost	1,293,000,000	[1],[3]	1,372,000,000	[1],[3]
Net unrealized losses recognized in AOCI	(191,000,000)	[3]	(206,000,000)	[3]
Carrying value	1,102,000,000	[2],[3]	1,166,000,000	[2],[3]
Gross unrecognized gains	93,000,000	[3]	60,000,000	[3]
Gross unrecognized losses	(2,000,000)	[3]	(20,000,000)	[3]
Fair value	1,193,000,000	[3]	1,206,000,000	[3]
Mortgage-backed securities - Commercial
Debt Securities Held-to-maturity
Amortized cost	11,000,000	[1],[3]	10,000,000	[1],[3]
Carrying value	11,000,000	[2],[3]	10,000,000	[2],[3]
Gross unrecognized gains	1,000,000	[3]	1,000,000	[3]
Fair value	12,000,000	[3]	11,000,000	[3]
Mortgage-backed securities
Debt Securities Held-to-maturity
Amortized cost	7,946,000,000	[1],[3]	2,835,000,000	[1],[3]
Net unrealized losses recognized in AOCI	(363,000,000)	[3]	(509,000,000)	[3]
Carrying value	7,583,000,000	[2],[3]	2,326,000,000	[2],[3]
Gross unrecognized gains	632,000,000	[3]	516,000,000	[3]
Gross unrecognized losses	(281,000,000)	[3]	(285,000,000)	[3]
Fair value	7,934,000,000	[3]	2,557,000,000	[3]
State and municipal securities
Schedule of Held-to-maturity Securities
Fair value of AFS securities transferred to HTM	6,400,000,000
Debt Securities Held-to-maturity
Amortized cost	8,339,000,000	[1]	1,394,000,000	[1],[4]
Net unrealized losses recognized in AOCI	(543,000,000)		(62,000,000)	[4]
Carrying value	7,796,000,000	[2]	1,332,000,000	[2],[4]
Gross unrecognized gains	271,000,000		50,000,000	[4]
Gross unrecognized losses	(218,000,000)		(70,000,000)	[4]
Fair value	7,849,000,000		1,312,000,000	[4]
Foreign government
Debt Securities Held-to-maturity
Amortized cost	5,641,000,000	[1]	5,628,000,000	[1]
Carrying value	5,641,000,000	[2]	5,628,000,000	[2]
Gross unrecognized gains	133,000,000		70,000,000
Gross unrecognized losses			(10,000,000)
Fair value	5,774,000,000		5,688,000,000
Corporate
Debt Securities Held-to-maturity
Amortized cost	816,000,000	[1]	818,000,000	[1]
Net unrealized losses recognized in AOCI	(65,000,000)		(78,000,000)
Carrying value	751,000,000	[2]	740,000,000	[2]
Gross unrecognized gains	120,000,000		111,000,000
Fair value	871,000,000		851,000,000
Asset-backed securities
Debt Securities Held-to-maturity
Amortized cost	580,000,000	[1],[3]	599,000,000	[1],[3]
Net unrealized losses recognized in AOCI	(21,000,000)	[3]	(26,000,000)	[3]
Carrying value	559,000,000	[2],[3]	573,000,000	[2],[3]
Gross unrecognized gains	50,000,000	[3]	22,000,000	[3]
Gross unrecognized losses	(10,000,000)	[3]	(10,000,000)	[3]
Fair value	$ 599,000,000	[3]	$ 585,000,000	[3]

[1] For securities transferred to HTM from Trading account assets, amortized cost is defined as the fair value of the securities at the date of transfer plus any accretion income and less any impairments recognized in earnings subsequent to transfer. For securities transferred to HTM from AFS, amortized cost is defined as the original purchase cost, adjusted for the cumulative accretion or amortization of any purchase discount or premium, plus or minus any cumulative fair value hedge adjustments, net of accretion or amortization, and less any other-than-temporary impairment recognized in earnings.

[2] HTM securities are carried on the Consolidated Balance Sheet at amortized cost, plus or minus any unamortized unrealized gains and losses and fair value hedge adjustments recognized in AOCI prior to reclassifying the securities from AFS to HTM. Changes in the values of these securities are not reported in the financial statements, except for the amortization of any difference between the carrying value at the transfer date and par value of the securities, and the recognition of any non-credit fair value adjustments in AOCI in connection with the recognition of any credit impairment in earnings related to securities the Company continues to intend to hold until maturity.

[3] The Company invests in mortgage-backed and asset-backed securities. These securitizations are generally considered VIEs. The Company’s maximum exposure to loss from these VIEs is equal to the carrying amount of the securities, which is reflected in the table above. For mortgage-backed and asset-backed securitizations in which the Company has other involvement, see Note 20 to the Consolidated Financial Statements.

[4] The net unrealized losses recognized in AOCI on state and municipal debt securities are primarily attributable to the effects of fair value hedge accounting applied when these debt securities were classified as AFS. Specifically, Citi hedged the LIBOR-benchmark interest rate component of certain fixed-rate tax-exempt state and municipal debt securities utilizing LIBOR-based interest rate swaps. During the hedge period, losses incurred on the LIBOR-hedging swaps recorded in earnings were substantially offset by gains on the state and municipal debt securities attributable to changes in the LIBOR swap rate being hedged. However, because the LIBOR swap rate decreased significantly during the hedge period while the overall fair value of the municipal debt securities was relatively unchanged, the effect of reclassifying fair value gains on these securities from AOCI to earnings attributable solely to changes in the LIBOR swap rate resulted in net unrealized losses remaining in AOCI that relate to the unhedged components of these securities. Upon transfer of these debt securities to HTM, all hedges have been de-designated and hedge accounting has ceased.