SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details 7) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013
Re-securitizations
Balance at beginning of period									$ 2,718,000,000
Balance at end of period	2,282,000,000				2,282,000,000				2,718,000,000
Mortgage servicing rights
Classification of Securitizations
Fair value of capitalized mortgage servicing rights	2,300,000,000		2,500,000,000		2,300,000,000		2,500,000,000
Principal amount of loans and other financial instruments	250,000,000,000		301,000,000,000		250,000,000,000		301,000,000,000
Re-securitizations
Balance at beginning of period	2,586,000,000		2,203,000,000		2,718,000,000		1,942,000,000
Originations	49,000,000		204,000,000		99,000,000		376,000,000
Changes in fair value of MSRs due to changes in inputs and assumptions	(91,000,000)		247,000,000		(175,000,000)		470,000,000
Other changes	(99,000,000)	[1]	(130,000,000)	[1]	(225,000,000)	[1]	(263,000,000)	[1]
Sale of MSRs	(163,000,000)		0		(135,000,000)	[2]	(1,000,000)	[2]
Balance at end of period	2,282,000,000		2,524,000,000		2,282,000,000		2,524,000,000
Servicing fees	162,000,000		198,000,000		332,000,000		415,000,000
Late fees	5,000,000		11,000,000		15,000,000		19,000,000
Ancillary fees	16,000,000		21,000,000		36,000,000		52,000,000
Total MSR fees	183,000,000		230,000,000		383,000,000		486,000,000
Non-agency-sponsored mortgages
Re-securitizations
Original par value of securities transferred to re-securitization entities	251,000,000		152,000,000		389,000,000		396,000,000
Fair value of re-securitizations deals in which the entity holds a retained interest	403,000,000				403,000,000				425,000,000
Market value of retained interest related to re-securitization transaction	40,000,000				40,000,000				131,000,000
Original par value of re-securitizations deals in which the entity holds a retained interest	5,100,000,000				5,100,000,000				6,100,000,000
Senior interests
Re-securitizations
Fair value of re-securitizations deals in which the entity holds a retained interest	27,000,000				27,000,000				58,000,000
Subordinated interests
Re-securitizations
Fair value of re-securitizations deals in which the entity holds a retained interest	376,000,000				376,000,000				367,000,000
U.S. government-sponsored agency guaranteed
Re-securitizations
Fair value of re-securitizations deals in which the entity holds a retained interest	1,200,000,000				1,200,000,000				1,500,000,000
Market value of retained interest related to re-securitization transaction	779,000,000				779,000,000				1,200,000,000
Securities transferred to re-securitization entities	4,900,000,000		7,300,000,000		11,300,000,000		14,800,000,000
Original fair value of re-securitizations deals in which the entity holds a retained interest	78,200,000,000				78,200,000,000				75,500,000,000
Citicorp | Mortgage servicing rights
Classification of Securitizations
Fair value of capitalized mortgage servicing rights	1,800,000,000				1,800,000,000
Citi Holdings | Mortgage servicing rights
Classification of Securitizations
Fair value of capitalized mortgage servicing rights			$ 1,900,000,000				$ 1,900,000,000

[1] Represents changes due to customer payments and passage of time.

[2] Includes a sale of credit challenged MSRs for which Citi paid the new servicer.