PREFERRED STOCK (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended	0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended	9 Months Ended		12 Months Ended		0 Months Ended		0 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2014 Forecast	Jan. 25, 2008 Series AA	Sep. 30, 2014 Series AA		Dec. 31, 2013 Series AA		Apr. 28, 2008 Series E	Sep. 30, 2014 Series E		Dec. 31, 2013 Series E		Oct. 29, 2012 Series A	Sep. 30, 2014 Series A		Dec. 31, 2013 Series A		Dec. 13, 2012 Series B	Sep. 30, 2014 Series B		Dec. 31, 2013 Series B		Mar. 26, 2013 Series C	Sep. 30, 2014 Series C		Dec. 31, 2013 Series C		Apr. 30, 2013 Series D	Sep. 30, 2014 Series D		Dec. 31, 2013 Series D		Sep. 19, 2013 Series J	Sep. 30, 2014 Series J		Dec. 31, 2013 Series J		Oct. 31, 2013 Series K	Sep. 30, 2014 Series K		Dec. 31, 2013 Series K		Feb. 12, 2014 Series L	Sep. 30, 2014 Series L		Dec. 31, 2013 Series L		Apr. 30, 2014 Series M	Sep. 30, 2014 Series M		Dec. 31, 2013 Series M		Oct. 29, 2014 Subsequent Event Series N	Oct. 29, 2014 Subsequent Event Series N	Oct. 29, 2014 3 Month LIBOR Subsequent Event Series N
Preferred stock
Dividend rate (as a percent)					8.125%	[1]	8.125%			8.40%	[2]	8.40%			5.95%	[3]	5.95%			5.90%	[4]	5.90%			5.80%	[5]	5.80%			5.35%	[6]	5.35%			7.125%	[7]	7.125%			6.875%	[8]	6.875%			6.875%	[9]	6.875%			6.30%	[10]	6.30%		5.80%
Redemption price per depositary share/ preference share (in dollars per share)					$ 25	[1]	$ 25			$ 1,000	[2]	$ 1,000			$ 1,000	[3]	$ 1,000			$ 1,000	[4]	$ 1,000			$ 25	[5]	$ 25			$ 1,000	[6]	$ 1,000			$ 25	[7]	$ 25			$ 25	[8]	$ 25			$ 25	[9]	$ 25			$ 1,000	[10]	$ 1,000
Number of depositary shares (in shares)					3,870,330	[1]	3,870,330			121,254	[2]	121,254			1,500,000	[3]	1,500,000			750,000	[4]	750,000			23,000,000	[5]	23,000,000			1,250,000	[6]	1,250,000			38,000,000	[7]	38,000,000			59,800,000	[8]	59,800,000			19,200,000	[9]	19,200,000			1,750,000	[10]	1,750,000			1,500,000,000
Carrying value	$ 8,968	$ 6,738			$ 97	[1]	$ 97	[1]		$ 121	[2]	$ 121	[2]		$ 1,500	[3]	$ 1,500	[3]		$ 750	[4]	$ 750	[4]		$ 575	[5]	$ 575	[5]		$ 1,250	[6]	$ 1,250	[6]		$ 950	[7]	$ 950	[7]		$ 1,495	[8]	$ 1,495	[8]		$ 480	[9]	$ 0	[9]		$ 1,750	[10]	$ 0	[10]
Depositary shares, interest in corresponding series of preferred stock				0.001					0.04					0.04					0.04					0.001					0.04					0.001					0.001					0.001					0.04					0.04
Distribution of preferred dividends	$ 352		$ 159
Preferred stock, dividend rate, spread on variable rate																																																								4.093%

[1] Issued as depositary shares, each representing a 1/1,000th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable quarterly on February 15, May 15, August 15 and November 15 when, as and if declared by the Citi Board of Directors.

[2] Issued as depositary shares, each representing a 1/25th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable semi-annually on April 30 and October 30 at a fixed rate until April 30, 2018, thereafter payable quarterly on January 30, April 30, July 30 and October 30 at a floating rate, in each case when, as and if declared by the Citi Board of Directors.

[3] Issued as depositary shares, each representing a 1/25th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable semi-annually on January 30 and July 30 at a fixed rate until January 30, 2023, thereafter payable quarterly on January 30, April 30, July 30 and October 30 at a floating rate, in each case when, as and if declared by the Citi Board of Directors.

[4] Issued as depositary shares, each representing a 1/25th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable semi-annually on February 15 and August 15 at a fixed rate until February 15, 2023, thereafter payable quarterly on February 15, May 15, August 15 and November 15 at a floating rate, in each case when, as and if declared by the Citi Board of Directors.

[5] Issued as depositary shares, each representing a 1/1,000th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable quarterly on January 22, April 22, July 22 and October 22 when, as and if declared by the Citi Board of Directors.

[6] Issued as depositary shares, each representing a 1/25th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable semi-annually on May 15 and November 15 at a fixed rate until May 15, 2023, thereafter payable quarterly on February 15, May 15, August 15 and November 15 at a floating rate, in each case when, as and if declared by the Citi Board of Directors.

[7] Issued as depositary shares, each representing a 1/1,000th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable quarterly on March 30, June 30, September 30 and December 30 at a fixed rate until September 30, 2023, thereafter payable quarterly on the same dates at a floating rate, in each case when, as and if declared by the Citi Board of Directors.

[8] Issued as depositary shares, each representing a 1/1,000th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable quarterly on February 15, May 15, August 15 and November 15 at a fixed rate until November 15, 2023, thereafter payable quarterly on the same dates at a floating rate, in each case when, as and if declared by the Citi Board of Directors.

[9] Issued as depositary shares, each representing a 1/1,000th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable quarterly on February 12, May 12, August 12 and November 12 at a fixed rate, in each case when, as and if declared by the Citi Board of Directors.

[10] Issued as depository shares, each representing a 1/25th interest in a share of the corresponding series of non-cumulative perpetual preferred stock. Dividends payable semi-annually on May 15 and November 15 at a fixed rate until May 15, 2024, thereafter payable quarterly on February 15, May 15, August 15, and November 15 at a floating rate, in each case when, as and if declared by the Citi Board of Directors.