EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
EARNINGS PER SHARE
Income from continuing operations before attribution of noncontrolling interests	$ 3,742		$ 2,601		$ 10,105		$ 9,578
Less: Noncontrolling interests from continuing operations	(28)		110		106		170
Net income from continuing operations (for EPS purposes)	3,770		2,491		9,999		9,408
Income (loss) from discontinued operations, net of taxes	1		(374)		112		(166)
Less: Noncontrolling interests from discontinued operations			(51)				(51)
Citigroup's net income	3,771		2,168		10,111		9,293
Less: Preferred dividends	4				17
Net income available to common shareholders	3,767		2,168		10,094		9,293
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares that contain nonforfeitable rights to dividends, applicable to basic EPS	70		20		164		78
Net income (loss) allocated to common shareholders for basic EPS	3,697		2,148		9,930		9,215
Add: Interest expense, net of tax, on convertible securities and adjustment of undistributed earnings allocated to employee restricted and deferred shares that contain nonforfeitable rights to dividends, applicable to diluted EPS	6		1		12		2
Net income allocated to common shareholders for diluted EPS	$ 3,703		$ 2,149		$ 9,942		$ 9,217
Weighted-average common shares outstanding applicable to basic EPS (in shares)	2,910.8		2,887.8		2,907.9		2,872.4
Effect of dilutive securities
TDECs (in shares)	87.6		87.6		87.6		87.8
Options (in shares)					1.0		0.1
Other employee plans (in shares)	0.1		2.4		0.8		1.8
Convertible securities (in shares)	0.1				0.1		0.1
Adjusted weighted-average common shares outstanding applicable to diluted EPS (in shares)	2,998.6	[1]	2,977.8	[1]	2,997.4	[1]	2,962.2	[1]
Basic earnings per share
Income from continuing operations (in dollars per share)	$ 1.27	[1],[2]	$ 0.85	[1],[2]	$ 3.38	[1],[2]	$ 3.25	[1],[2]
Discontinued operations (in dollars per share)			$ (0.11)	[1],[2]	$ 0.04	[1],[2]	$ (0.04)	[1],[2]
Net income (in dollars per share)	$ 1.27	[1],[2]	$ 0.74	[1],[2]	$ 3.41	[1],[2]	$ 3.21	[1],[2]
Diluted earnings per share
Income from continuing operations (in dollars per share)	$ 1.23	[1],[2]	$ 0.83	[1],[2]	$ 3.28	[1],[2]	$ 3.15	[1],[2]
Discontinued operations (in dollars per share)			$ (0.11)	[1],[2]	$ 0.04	[1],[2]	$ (0.04)	[1],[2]
Net income (in dollars per share)	$ 1.23	[1],[2]	$ 0.72	[1],[2]	$ 3.32	[1],[2]	$ 3.11	[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)	38.1		38.5
Antidilutive securities weighted average exercise price (in dollars per share)	$ 71.24		$ 95.80		$ 71.24		$ 95.80
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 weighted average 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
Antidilutive securities excluded from computation of earnings per common share (in shares)	5.9		11.8
Antidilutive securities weighted average exercise price (in dollars per share)			$ 318.30				$ 318.30

[1] Earnings per share and adjusted weighted average common shares outstanding for all periods reflect Citigroup's 1-for-10 reverse stock split, which was effective May 6, 2011.

[2] Due to rounding, earnings per share on continuing operations and discontinued operations may not sum to earnings per share amount on net income.