EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended				3 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012 Weighted-average options to purchase common stock	Jun. 30, 2011 Weighted-average options to purchase common stock	Jun. 30, 2012 Warrants issued to U.S. Treasury as part of TARP and loss-sharing agreement	Jun. 30, 2011 Warrants issued to U.S. Treasury as part of TARP and loss-sharing agreement	Sep. 30, 2011 Equity units convertible into common stock held by the Abu Dhabi Investment Authority (ADIA)	Jun. 30, 2011 Equity units convertible into common stock held by the Abu Dhabi Investment Authority (ADIA)
EARNINGS PER SHARE
Income from continuing operations before attribution of noncontrolling interests	$ 2,987		$ 3,332		$ 6,049		$ 6,363
Less: Noncontrolling interests from continuing operations	40		62		166		134
Net income from continuing operations (for EPS purposes)	2,947		3,270		5,883		6,229
Income (loss) from discontinued operations, net of taxes	(1)		71		(6)		111
Citigroup's net income	2,946		3,341		5,877		6,340
Less: Preferred dividends	9		9		13		13
Net income available to common shareholders	2,937		3,332		5,864		6,327
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares that contain nonforfeitable rights to dividends, applicable to basic EPS	69		62		123		96
Net income (loss) allocated to common shareholders for basic EPS	2,868		3,270		5,741		6,231
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	4		6		8		7
Net income allocated to common shareholders for diluted EPS	$ 2,872		$ 3,276		$ 5,749		$ 6,238
Weighted-average common shares outstanding applicable to basic EPS	2,926.6		2,908.6		2,926.4		2,906.5
Effect of dilutive securities
T-DECs (in shares)	87.8		87.6		87.8		87.6
Other employee plans (in shares)	0.5		0.1		0.5		1.1
Convertible securities (in shares)	0.1		0.1		0.1		0.1
Options (in shares)			0.6				1.5
Adjusted weighted-average common shares outstanding applicable to diluted EPS	3,015.0	[1]	2,997.0	[1]	3,014.8	[1]	2,996.8	[1]
Basic earnings per share
Income from continuing operations (in dollars per share)	$ 0.98	[1],[2]	$ 1.10	[1],[2]	$ 1.96	[1],[2]	$ 2.11	[1],[2]
Discontinued operations (in dollars per share)			$ 0.02	[1],[2]			$ 0.04	[1],[2]
Net income (in dollars per share)	$ 0.98	[1],[2]	$ 1.12	[1],[2]	$ 1.96	[1],[2]	$ 2.14	[1],[2]
Diluted earnings per share
Income from continuing operations (in dollars per share)	$ 0.95	[1],[2]	$ 1.07	[1],[2]	$ 1.91	[1],[2]	$ 2.05	[1],[2]
Discontinued operations (in dollars per share)			$ 0.02	[1],[2]			$ 0.04	[1],[2]
Net income (in dollars per share)	$ 0.95	[1],[2]	$ 1.09	[1],[2]	$ 1.91	[1],[2]	$ 2.08	[1],[2]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per common share (in shares)									35.8	10.8	21.0	25.5		5.9
Number of common stocks issued to convert equity units													5.9
Antidilutive securities weighted average exercise price (in dollars per share)									$ 52.80	$ 160.86
Antidilutive securities exercise price (in dollars per share)											$ 178.50	$ 106.10		$ 318.30

[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.