SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details 6) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Cash Flows Between Transferor and Transferee
Gains (losses) recognized on the securitization			$ 0
U.S. government-sponsored agency guaranteed | Citicorp
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	15,400,000,000	13,800,000,000	54,200,000,000	40,700,000,000
Contractual servicing fees received	100,000,000	100,000,000	300,000,000	400,000,000
Cash flows received on retained interests and other net cash flows				100,000,000
Gains (losses) recognized on the securitization	3,300,000	2,500,000	147,400,000	8,400,000
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Weighted average discount rate, date of sale or securitization (as a percent)	10.00%	12.00%	10.00%	11.40%
Weighted average constant prepayment rate, date of sale or securitization (as a percent)	4.50%	10.80%	5.30%	10.20%
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)			6.40%		6.10%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)			12.50%		27.70%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	2,650,000,000		2,650,000,000		1,987,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(72,000,000)		(72,000,000)		(46,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(140,000,000)		(140,000,000)		(90,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(99,000,000)		(99,000,000)		(110,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(192,000,000)		(192,000,000)		(211,000,000)
U.S. government-sponsored agency guaranteed | Citicorp | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)	0.80%	0.20%	0.80%	0.20%
Constant prepayment rate, date of sale or securitization (as a percent)	2.40%	9.40%	2.40%	7.30%
Weighted average life, date of sale or securitization	5 years 3 months 18 days	2 years 4 months 24 days	1 month 6 days	1 year 9 months 18 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			0.00%		0.60%
Constant prepayment rate, transferor's continuing involvement (as a percent)			6.00%		9.00%
Weighted average life, transferor's continuing involvement			3 years 2 months 12 days		3 months 18 days
U.S. government-sponsored agency guaranteed | Citicorp | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)	12.20%	12.90%	12.40%	14.40%
Constant prepayment rate, date of sale or securitization (as a percent)	19.00%	36.40%	21.40%	36.40%
Weighted average life, date of sale or securitization	8 years 4 months 24 days	6 years 3 months 18 days	11 years 9 months 18 days	11 years 9 months 18 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			21.40%		17.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)			23.70%		57.80%
Weighted average life, transferor's continuing involvement			27 years 1 month 6 days		18 years 3 months 18 days
U.S. government-sponsored agency guaranteed | Citi Holdings
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	100,000,000	100,000,000	100,000,000	300,000,000
Contractual servicing fees received	100,000,000	100,000,000	200,000,000	300,000,000
Gains (losses) recognized on the securitization	7,200,000	8,900,000	14,100,000	39,700,000
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)			11.90%		9.70%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)			21.30%		28.60%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	563,000,000		563,000,000		618,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(20,000,000)		(20,000,000)		(22,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(39,000,000)		(39,000,000)		(42,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(34,000,000)		(34,000,000)		(57,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(66,000,000)		(66,000,000)		(109,000,000)
U.S. government-sponsored agency guaranteed | Citi Holdings | Low end of range
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			0.00%		0.00%
Constant prepayment rate, transferor's continuing involvement (as a percent)			7.70%		8.20%
Weighted average life, transferor's continuing involvement			2 years 3 months 18 days		2 years 2 months 12 days
U.S. government-sponsored agency guaranteed | Citi Holdings | High end of range
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			53.80%		52.70%
Constant prepayment rate, transferor's continuing involvement (as a percent)			28.70%		37.40%
Weighted average life, transferor's continuing involvement			7 years 9 months 18 days		7 years 9 months 18 days
Non-agency-sponsored mortgages | Citicorp
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	2,000,000,000	1,500,000,000	5,000,000,000	2,000,000,000
Gains (losses) recognized on the securitization	12,900,000	21,900,000	44,500,000	20,400,000
Senior interests | Citicorp
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)	3.90%			13.40%
Weighted average discount rate, date of sale or securitization (as a percent)	3.90%		3.40%	13.40%
Constant prepayment rate, date of sale or securitization (as a percent)	5.40%			8.10%
Weighted average constant prepayment rate, date of sale or securitization (as a percent)	5.40%		7.20%	8.10%
Anticipated net credit losses, date of sale or securitization (as a percent)	47.80%			50.50%
Weighted average anticipated net credit losses, date of sale or securitization (as a percent)	47.80%		49.30%	50.50%
Weighted average life, date of sale or securitization	7 years			9 years
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)			7.20%		9.00%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)			5.40%		12.30%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)			60.00%		47.00%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	187,000,000		187,000,000		88,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(4,000,000)		(4,000,000)		(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(8,000,000)		(8,000,000)		(4,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(1,000,000)		(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(3,000,000)		(3,000,000)		(3,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(1,000,000)		(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(3,000,000)		(3,000,000)		(3,000,000)
Senior interests | Citicorp | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)			2.30%
Constant prepayment rate, date of sale or securitization (as a percent)			5.40%
Anticipated net credit losses, date of sale or securitization (as a percent)			47.20%
Weighted average life, date of sale or securitization			2 years 10 months 24 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			0.50%		1.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)			1.60%		1.90%
Anticipated credit losses, transferor's continuing involvement (as a percent)			0.10%		0.10%
Weighted average life, transferor's continuing involvement			3 months 18 days		4 months 24 days
Senior interests | Citicorp | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)			4.30%
Constant prepayment rate, date of sale or securitization (as a percent)			10.00%
Anticipated net credit losses, date of sale or securitization (as a percent)			53.00%
Weighted average life, date of sale or securitization			9 years 8 months 12 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			17.30%		24.00%
Constant prepayment rate, transferor's continuing involvement (as a percent)			100.00%		24.90%
Anticipated credit losses, transferor's continuing involvement (as a percent)			81.20%		80.20%
Weighted average life, transferor's continuing involvement			13 years		11 years 2 months 12 days
Senior interests | Citi Holdings
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)			16.80%		4.20%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)			16.10%		21.70%
Anticipated credit losses, transferor's continuing involvement (as a percent)			0.20%		0.50%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)			0.20%		0.50%
Weighted average life, transferor's continuing involvement			5 years 1 month 6 days
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	46,000,000		46,000,000		39,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(3,000,000)		(3,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(5,000,000)		(5,000,000)		(1,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(1,000,000)		(1,000,000)		(3,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(2,000,000)		(2,000,000)		(7,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(8,000,000)		(8,000,000)		(9,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(16,000,000)		(16,000,000)		(19,000,000)
Senior interests | Citi Holdings | Low end of range
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			10.00%		4.10%
Constant prepayment rate, transferor's continuing involvement (as a percent)			12.70%		21.70%
Weighted average life, transferor's continuing involvement					2 years 1 month 6 days
Senior interests | Citi Holdings | High end of range
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			16.90%		29.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)			28.70%		26.00%
Weighted average life, transferor's continuing involvement					4 years 4 months 24 days
Subordinated interests | Citicorp
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Weighted average discount rate, date of sale or securitization (as a percent)	6.10%	9.00%	7.60%	13.20%
Weighted average constant prepayment rate, date of sale or securitization (as a percent)	6.80%	6.60%	6.90%	4.70%
Weighted average anticipated net credit losses, date of sale or securitization (as a percent)	29.60%	44.00%	49.30%	54.30%
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)			11.40%		13.80%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)			7.10%		10.00%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)			50.70%		54.10%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	408,000,000		408,000,000		466,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(25,000,000)		(25,000,000)		(31,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(47,000,000)		(47,000,000)		(59,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(5,000,000)		(5,000,000)		(11,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(11,000,000)		(11,000,000)		(22,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(6,000,000)		(6,000,000)		(13,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(13,000,000)		(13,000,000)		(24,000,000)
Subordinated interests | Citicorp | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)	0.10%	4.60%	0.10%	4.60%
Constant prepayment rate, date of sale or securitization (as a percent)	0.10%	3.80%	0.10%	2.20%
Anticipated net credit losses, date of sale or securitization (as a percent)	0.10%	35.00%	0.10%	35.00%
Weighted average life, date of sale or securitization	10 years	2 years 6 months	2 years 6 months	2 years 6 months
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			0.10%		1.10%
Constant prepayment rate, transferor's continuing involvement (as a percent)			0.10%		0.50%
Anticipated credit losses, transferor's continuing involvement (as a percent)			23.90%		33.40%
Weighted average life, transferor's continuing involvement			0 years		0 years
Subordinated interests | Citicorp | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)	9.80%	17.20%	19.20%	19.30%
Constant prepayment rate, date of sale or securitization (as a percent)	11.20%	8.40%	11.20%	8.40%
Anticipated net credit losses, date of sale or securitization (as a percent)	49.00%	60.00%	89.00%	62.90%
Weighted average life, date of sale or securitization	10 years 2 months 12 days	13 years 1 month 6 days	16 years 6 months	13 years 1 month 6 days
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			20.00%		29.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)			31.20%		29.40%
Anticipated credit losses, transferor's continuing involvement (as a percent)			83.50%		90.00%
Weighted average life, transferor's continuing involvement			23 years		25 years 8 months 12 days
Subordinated interests | Citi Holdings
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)			12.10%		8.00%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)			7.10%		15.70%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)			51.30%		50.10%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	16,000,000		16,000,000		16,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(1,000,000)		(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(3,000,000)		(3,000,000)		(2,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(1,000,000)		(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(1,000,000)		(1,000,000)		(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(1,000,000)		(1,000,000)		(4,000,000)
Subordinated interests | Citi Holdings | Low end of range
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			8.80%		3.40%
Constant prepayment rate, transferor's continuing involvement (as a percent)			7.00%		12.70%
Anticipated credit losses, transferor's continuing involvement (as a percent)			49.50%		50.00%
Weighted average life, transferor's continuing involvement			10 years 1 month 6 days		6 years
Subordinated interests | Citi Holdings | High end of range
Key assumptions used in measuring fair value related to transferor's continuing involvement
Discount rate, transferor's continuing involvement (as a percent)			15.30%		12.40%
Constant prepayment rate, transferor's continuing involvement (as a percent)			7.20%		18.70%
Anticipated credit losses, transferor's continuing involvement (as a percent)			53.10%		50.10%
Weighted average life, transferor's continuing involvement			10 years 6 months		7 years 4 months 24 days
Collateralized debt obligations (CDOs) | Citi Holdings
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	17,000,000		17,000,000		16,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(1,000,000)		(1,000,000)		(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(2,000,000)		(2,000,000)		(3,000,000)
Collateralized debt obligations (CDOs) | Citi Holdings | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)			44.30%		46.90%
Collateralized debt obligations (CDOs) | Citi Holdings | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)			48.70%		51.60%
Collateralized loan obligations (CLOs) | Citi Holdings
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	1,373,000,000		1,373,000,000		428,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(9,000,000)		(9,000,000)		(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(18,000,000)		(18,000,000)		(4,000,000)
Collateralized loan obligations (CLOs) | Citi Holdings | Low end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)			1.60%		1.90%
Collateralized loan obligations (CLOs) | Citi Holdings | High end of range
Key assumptions used in measuring fair value of retained interests at date of sale or securitization of mortgage receivables
Discount rate, date of sale or securitization (as a percent)			1.70%		2.10%
Asset-based financing | Citicorp
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	1,326,000,000		1,326,000,000		1,726,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(12,000,000)		(12,000,000)		(22,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(24,000,000)		(24,000,000)		(44,000,000)
Asset-based financing | Citi Holdings
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	$ 95,000,000		$ 95,000,000		$ 339,000,000