SECURITIZATIONS AND VARIABLE INTEREST ENTITIES (Details 6) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 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	18,300,000,000	16,600,000,000
Contractual servicing fees received	100,000,000	100,000,000
Gains (losses) recognized on the securitization	1,000,000	3,000,000
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)	10.90%	11.00%
Weighted average constant prepayment rate, date of sale or securitization (as a percent)	5.80%	10.70%
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)	6.50%		6.10%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)	20.30%		27.70%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	2,148,000,000		1,987,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(56,000,000)		(46,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(108,000,000)		(90,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(110,000,000)		(110,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(207,000,000)		(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)	2.60%	2.30%
Constant prepayment rate, date of sale or securitization (as a percent)	4.00%	7.30%
Weighted average life, date of sale or securitization	6 years 4 months 24 days	6 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)	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	4 months 24 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)	12.40%	12.90%
Constant prepayment rate, date of sale or securitization (as a percent)	21.40%	13.40%
Weighted average life, date of sale or securitization	10 years 4 months 24 days	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)	29.10%		17.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)	48.30%		57.80%
Weighted average life, transferor's continuing involvement	18 years 10 months 24 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		200,000,000
Contractual servicing fees received	100,000,000	100,000,000
Gains (losses) recognized on the securitization	3,000,000	20,000,000
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)	11.50%		9.70%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)	25.40%		28.60%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	625,000,000		618,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(22,000,000)		(22,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(43,000,000)		(42,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(48,000,000)		(57,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(93,000,000)		(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)	7.20%		8.20%
Weighted average life, transferor's continuing involvement	2 years 2 months 12 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)	51.00%		52.70%
Constant prepayment rate, transferor's continuing involvement (as a percent)	31.60%		37.40%
Weighted average life, transferor's continuing involvement	7 years 10 months 24 days		7 years 9 months 18 days
Non-agency-sponsored mortgages | Citicorp
Cash Flows Between Transferor and Transferee
Proceeds from new securitizations	400,000,000	300,000,000
Gains (losses) recognized on the securitization	8,000,000	(1,000,000)
Senior interests | Citicorp
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)	9.60%		9.00%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)	9.80%		12.30%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)	52.50%		47.00%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	107,000,000		88,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(4,000,000)		(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(7,000,000)		(4,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(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)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(3,000,000)		(3,000,000)
Senior interests | Citicorp | 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)	1.20%		1.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)	1.20%		1.90%
Anticipated credit losses, transferor's continuing involvement (as a percent)	0.10%		0.10%
Weighted average life, transferor's continuing involvement	1 year 8 months 12 days		4 months 24 days
Senior interests | Citicorp | 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)	53.70%		24.00%
Constant prepayment rate, transferor's continuing involvement (as a percent)	25.80%		24.90%
Anticipated credit losses, transferor's continuing involvement (as a percent)	84.80%		80.20%
Weighted average life, transferor's continuing involvement	11 years 10 months 24 days		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)	12.90%		4.20%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)	19.00%		21.70%
Anticipated credit losses, transferor's continuing involvement (as a percent)	0.30%		0.50%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)	0.30%		0.50%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	59,000,000		39,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(3,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(6,000,000)		(1,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(3,000,000)		(3,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(7,000,000)		(7,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(1,000,000)		(9,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(1,000,000)		(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)	9.10%		4.10%
Constant prepayment rate, transferor's continuing involvement (as a percent)	17.40%		21.70%
Weighted average life, transferor's continuing involvement	2 years 1 month 6 days		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)	32.10%		29.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)	24.10%		26.00%
Weighted average life, transferor's continuing involvement	4 years 8 months 12 days		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)	8.30%	18.30%
Weighted average constant prepayment rate, date of sale or securitization (as a percent)	2.80%	3.30%
Weighted average anticipated net credit losses, date of sale or securitization (as a percent)	80.70%	59.10%
Key assumptions used in measuring fair value related to transferor's continuing involvement
Weighted average discount rate, transferor's continuing involvement (as a percent)	13.80%		13.80%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)	9.40%		10.00%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)	53.40%		54.10%
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	403,000,000		466,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(28,000,000)		(31,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(54,000,000)		(59,000,000)
Carrying value of retained interests, impact of 10% adverse change in constant prepayment rate	(9,000,000)		(11,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(19,000,000)		(22,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(12,000,000)		(13,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(22,000,000)		(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)	5.90%	16.90%
Constant prepayment rate, date of sale or securitization (as a percent)	1.30%	2.20%
Anticipated net credit losses, date of sale or securitization (as a percent)	44.70%	55.20%
Weighted average life, date of sale or securitization	6 years 6 months	5 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)	5.50%		1.10%
Constant prepayment rate, transferor's continuing involvement (as a percent)	0.50%		0.50%
Anticipated credit losses, transferor's continuing involvement (as a percent)	27.40%		33.40%
Weighted average life, transferor's continuing involvement	1 month 6 days		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)	19.20%	19.30%
Constant prepayment rate, date of sale or securitization (as a percent)	9.70%	5.40%
Anticipated net credit losses, date of sale or securitization (as a percent)	89.00%	62.90%
Weighted average life, date of sale or securitization	16 years 6 months	6 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)	60.30%		29.20%
Constant prepayment rate, transferor's continuing involvement (as a percent)	33.40%		29.40%
Anticipated credit losses, transferor's continuing involvement (as a percent)	90.00%		90.00%
Weighted average life, transferor's continuing involvement	21 years 10 months 24 days		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)	10.30%		8.00%
Weighted average constant prepayment rate, transferor's continuing involvement (as a percent)	13.50%		15.70%
Weighted average anticipated credit losses, transferor's continuing involvement (as a percent)	52.60%		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
Carrying value of retained interests, impact of 10% adverse change in discount rate	(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(2,000,000)		(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in constant prepayment rate	(1,000,000)		(1,000,000)
Carrying value of retained interests, impact of 10% adverse change in anticipated net credit losses	(1,000,000)		(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in anticipated net credit losses	(2,000,000)		(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)	6.20%		3.40%
Constant prepayment rate, transferor's continuing involvement (as a percent)	11.60%		12.70%
Anticipated credit losses, transferor's continuing involvement (as a percent)	50.70%		50.00%
Weighted average life, transferor's continuing involvement	7 years 9 months 18 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)	14.30%		12.40%
Constant prepayment rate, transferor's continuing involvement (as a percent)	15.30%		18.70%
Anticipated credit losses, transferor's continuing involvement (as a percent)	54.50%		50.10%
Weighted average life, transferor's continuing involvement	8 years 3 months 18 days		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	16,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(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)	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)	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	203,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(2,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(3,000,000)
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)	2.30%
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)	2.50%
Asset-based financing | Citicorp
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	1,421,000,000
Carrying value of retained interests, impact of 10% adverse change in discount rate	(16,000,000)
Carrying value of retained interests, impact of 20% adverse change in discount rate	(32,000,000)
Asset-based financing | Citi Holdings
Sensitivity analysis of fair value of interests continued to be held by transferor
Carrying value of retained interests	$ 338,000,000