EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended				9 Months Ended
	May 06, 2011	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
EARNINGS PER SHARE
Income from continuing operations before attribution of noncontrolling interests		$ 524		$ 3,742		$ 6,573		$ 10,105
Less: Noncontrolling interests from continuing operations		25		(28)		191		106
Net income from continuing operations (for EPS purposes)		499		3,770		6,382		9,999
Income (loss) from discontinued operations, net of taxes		(31)		1		(37)		112
Citigroup's net income		468		3,771		6,345		10,111
Less: Preferred dividends		4		4		17		17
Net income available to common shareholders		464		3,767		6,328		10,094
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares that contain nonforfeitable rights to dividends, applicable to basic EPS		11		70		138		164
Net income allocated to common shareholders for basic		453		3,697		6,190		9,930
Add: Interest expense, net of tax, on convertible securities and adjustment of undistributed earnings allocated to employee restricted and deferred shares with nonforfeitable rights to dividends, applicable to diluted EPS		2		6		10		12
Net income allocated to common shareholders for diluted EPS		$ 455		$ 3,703		$ 6,200		$ 9,942
Weighted-average common shares outstanding applicable to basic EPS		2,926.8		2,910.8		2,926.5		2,907.9
Reverse stock split effective May 6, 2011	0.1
Effect of dilutive securities
T-DECs (in shares)		87.8		87.6		87.8		87.6
Other employee plans (in shares)		0.6		0.1		0.5		0.8
Convertible securities (in shares)		0.1		0.1		0.1		0.1
Options (in shares)								1.0
Adjusted weighted-average common shares outstanding applicable to diluted EPS		3,015.3	[1]	2,998.6	[1]	3,014.9	[1]	2,997.4	[1]
Basic earnings per share
Income from continuing operations (in dollars per share)		$ 0.17	[1],[2]	$ 1.27	[1],[2]	$ 2.13	[1],[2]	$ 3.38	[1],[2]
Discontinued operations (in dollars per share)		$ (0.01)	[1],[2]			$ (0.01)	[1],[2]	$ 0.04	[1],[2]
Net income (in dollars per share)		$ 0.15	[1],[2]	$ 1.27	[1],[2]	$ 2.12	[1],[2]	$ 3.41	[1],[2]
Diluted earnings per share
Income from continuing operations (in dollars per share)		$ 0.16	[1],[2]	$ 1.23	[1],[2]	$ 2.07	[1],[2]	$ 3.28	[1],[2]
Discontinued operations (in dollars per share)		$ (0.01)	[1],[2]			$ (0.01)	[1],[2]	$ 0.04	[1],[2]
Net income (in dollars per share)		$ 0.15	[1],[2]	$ 1.23	[1],[2]	$ 2.06	[1],[2]	$ 3.32	[1],[2]
Weighted-average options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per common share (in shares)		35.6		38.1
Antidilutive securities weighted average exercise price (in dollars per share)		$ 51.97		$ 71.24		$ 51.97		$ 71.24
Warrants issued to U.S. Treasury as part of TARP and loss-sharing agreement
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per common share (in shares)		21.0		25.5
Antidilutive securities exercise price (in dollars per share)		$ 178.50		$ 106.10		$ 178.50		$ 106.10
Equity units convertible into common stock held by the Abu Dhabi Investment Authority (ADIA)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Number of common stocks issued to convert equity units				5.9

[1] Due to rounding, earnings per share on continuing operations and Discontinued operations may not sum to earnings per share on net income.

[2] All per share amounts and Citigroup shares outstanding for all periods reflect Citigroup's 1-for-10 reverse stock split, which was effective May 6, 2011.