INVESTMENTS (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013
Investment Holdings
Investments	$ 333,047			$ 333,047			$ 308,980
Interest and dividends on investments
Taxable interest	1,627		1,389	4,638		4,280
Interest exempt from U.S. federal income tax	96		197	407		567
Dividends	101		103	343		331
Total interest and dividends	1,824		1,689	5,388		5,178
Gross realized investments losses, excluding losses from other-than-temporary impairment
Gross realized investment gains	229		375	689		1,489
Gross realized investment losses	(93)		(312)	(341)		(725)
Net realized gains (losses)	136		63	348		764
Available-for-sale Securities transferred from Held-to-maturity
Carrying value of HTM securities sold	0		235	5		720
Net realized gain (loss) on sale of held-to-maturity securities			(39)			(105)
Carrying value of securities reclassified as available-for-sale	700		0	766		902
OTTI losses on securities reclassified to available-for-sale	(2)		0	(11)		(155)
Securities available-for-sale
Amortized cost	298,551			298,551			288,567
Gross unrealized gains	2,248	[1]		2,248	[1]		2,028	[1]
Gross unrealized losses	2,121	[1]		2,121	[1]		4,084	[1]
Fair value	298,678			298,678			286,511
Unrealized gains from impact of minority investments and the related allocations and pick up of unrealized gains and losses of AFS securities	16			16			36
Mortgage-backed securities - U.S. agency-sponsored
Securities available-for-sale
Amortized cost	36,654	[2]		36,654	[2]		42,494	[2]
Gross unrealized gains	522	[1],[2]		522	[1],[2]		391	[1],[2]
Gross unrealized losses	308	[1],[2]		308	[1],[2]		888	[1],[2]
Fair value	36,868	[2]		36,868	[2]		41,997	[2]
Mortgage-backed securities - Prime
Securities available-for-sale
Amortized cost	13	[2]		13	[2]		33	[2]
Gross unrealized gains							2	[1],[2]
Gross unrealized losses							3	[1],[2]
Fair value	13	[2]		13	[2]		32	[2]
Mortgage-backed securities - Alt-A
Securities available-for-sale
Amortized cost	2	[2]		2	[2]		84	[2]
Gross unrealized gains							10	[1],[2]
Fair value	2	[2]		2	[2]		94	[2]
Mortgage-backed securities - Subprime
Securities available-for-sale
Amortized cost	0	[2]		0	[2]		12	[2]
Fair value	0	[2]		0	[2]		12	[2]
Mortgage-backed securities - Non-U.S. residential
Securities available-for-sale
Amortized cost	9,200	[2]		9,200	[2]		9,976	[2]
Gross unrealized gains	84	[1],[2]		84	[1],[2]		95	[1],[2]
Gross unrealized losses	9	[1],[2]		9	[1],[2]		4	[1],[2]
Fair value	9,275	[2]		9,275	[2]		10,067	[2]
Mortgage-backed securities - Commercial
Securities available-for-sale
Amortized cost	562	[2]		562	[2]		455	[2]
Gross unrealized gains	6	[1],[2]		6	[1],[2]		6	[1],[2]
Gross unrealized losses	4	[1],[2]		4	[1],[2]		8	[1],[2]
Fair value	564	[2]		564	[2]		453	[2]
Mortgage-backed securities
Securities available-for-sale
Amortized cost	46,431	[2]		46,431	[2]		53,054	[2]
Gross unrealized gains	612	[1],[2]		612	[1],[2]		504	[1],[2]
Gross unrealized losses	321	[1],[2]		321	[1],[2]		903	[1],[2]
Fair value	46,722	[2]		46,722	[2]		52,655	[2]
U.S. Treasury
Securities available-for-sale
Amortized cost	95,175			95,175			68,891
Gross unrealized gains	356	[1]		356	[1]		476	[1]
Gross unrealized losses	190	[1]		190	[1]		147	[1]
Fair value	95,341			95,341			69,220
Agency obligations
Securities available-for-sale
Amortized cost	16,513			16,513			18,320
Gross unrealized gains	61	[1]		61	[1]		123	[1]
Gross unrealized losses	29	[1]		29	[1]		67	[1]
Fair value	16,545			16,545			18,376
U.S. Treasury and federal agency securities
Securities available-for-sale
Amortized cost	111,688			111,688			87,211
Gross unrealized gains	417	[1]		417	[1]		599	[1]
Gross unrealized losses	219	[1]		219	[1]		214	[1]
Fair value	111,886			111,886			87,596
State and municipal securities
Securities available-for-sale
Amortized cost	13,894	[3]		13,894	[3]		20,761	[3]
Gross unrealized gains	144	[1],[3]		144	[1],[3]		184	[1],[3]
Gross unrealized losses	1,125	[1],[3]		1,125	[1],[3]		2,005	[1],[3]
Fair value	12,913	[3]		12,913	[3]		18,940	[3]
Foreign government
Securities available-for-sale
Amortized cost	95,314			95,314			96,608
Gross unrealized gains	639	[1]		639	[1]		403	[1]
Gross unrealized losses	293	[1]		293	[1]		540	[1]
Fair value	95,660			95,660			96,471
Corporate
Securities available-for-sale
Amortized cost	13,767			13,767			11,039
Gross unrealized gains	290	[1]		290	[1]		210	[1]
Gross unrealized losses	99	[1]		99	[1]		119	[1]
Fair value	13,958			13,958			11,130
Asset-backed securities
Securities available-for-sale
Amortized cost	12,830	[2]		12,830	[2]		15,352	[2]
Gross unrealized gains	41	[1],[2]		41	[1],[2]		42	[1],[2]
Gross unrealized losses	28	[1],[2]		28	[1],[2]		120	[1],[2]
Fair value	12,843	[2]		12,843	[2]		15,274	[2]
Other debt securities
Securities available-for-sale
Amortized cost	711			711			710
Gross unrealized gains							1	[1]
Gross unrealized losses	1	[1]		1	[1]
Fair value	710			710			711
Debt securities
Securities available-for-sale
Amortized cost	294,635			294,635			284,735
Gross unrealized gains	2,143	[1]		2,143	[1]		1,943	[1]
Gross unrealized losses	2,086	[1]		2,086	[1]		3,901	[1]
Fair value	294,692			294,692			282,777
Equity securities
Securities available-for-sale
Amortized cost	3,916			3,916			3,832
Gross unrealized gains	105	[1]		105	[1]		85	[1]
Gross unrealized losses	35	[1]		35	[1]		183	[1]
Fair value	3,986			3,986			3,734
Securities available-for-sale (AFS)
Investment Holdings
Investments	298,678			298,678			286,511
Held-to-maturity Securities
Investment Holdings
Investments	24,038	[4]		24,038	[4]		10,599	[4]
Non-marketable equity securities | Fair value
Investment Holdings
Investments	3,504	[5]		3,504	[5]		4,705	[5]
Non-marketable equity securities | Carried at cost
Investment Holdings
Investments	$ 6,827	[6]		$ 6,827	[6]		$ 7,165	[6]

[1] Gross unrealized gains and losses, as presented, do not include the impact of minority investments and the related allocations and pick-up of unrealized gains and losses of AFS securities. These amounts totaled $16 million of unrealized gains and $36 million of unrealized gains as of September 30, 2014 and December 31, 2013, respectively.

[2] 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.

[3] The gross unrealized losses on state and municipal debt securities are primarily attributable to the effects of fair value hedge accounting. Specifically, Citi hedges 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 Accumulated other comprehensive income (loss) (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.

[4] Recorded at amortized cost less impairment for securities that have credit-related impairment.

[5] Unrealized gains and losses for non-marketable equity securities carried at fair value are recognized in earnings.

[6] Non-marketable equity securities carried at cost primarily consist of shares issued by the Federal Reserve Bank, Federal Home Loan Banks, foreign central banks and various clearing houses of which Citigroup is a member.