EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2012 Weighted-average options to purchase common stock	Mar. 31, 2011 Weighted-average options to purchase common stock	Mar. 31, 2012 Warrants issued to U.S. Treasury as part of TARP and loss-sharing agreement	Mar. 31, 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)	Mar. 31, 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	$ 3,062		$ 3,031
Less: Noncontrolling interests from continuing operations	126		72
Net income from continuing operations (for EPS purposes)	2,936		2,959
Income (loss) from discontinued operations, net of taxes	(5)		40
Citigroup's net income	2,931		2,999
Less: Preferred dividends	4		4
Net income available to common shareholders	2,927		2,995
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares with nonforfeitable rights to dividends, applicable to basic EPS	54		35
Net income allocated to common shareholders for basic EPS	2,873		2,960
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		1
Net income allocated to common shareholders for diluted EPS	$ 2,877		$ 2,961
Weighted-average common shares outstanding applicable to basic EPS (in shares)	2,926.2		2,904.4
Effect of dilutive securities
TDECs (in shares)	87.7		87.6
Options (in shares)			2.5
Other employee plans (in shares)	0.5		2.0
Convertible securities (in shares)	0.1		0.1
Adjusted weighted-average common shares outstanding applicable to diluted EPS	3,014.5	[1]	2,996.6	[1]
Basic earnings per share
Income from continuing operations (in dollars per share)	$ 0.98	[1],[2]	$ 1.01	[1],[2]
Discontinued operations (in dollars per share)			$ 0.01	[1],[2]
Net income (in dollars per share)	$ 0.98	[1],[2]	$ 1.02	[1],[2]
Diluted earnings per share
Income from continuing operations (in dollars per share)	$ 0.96	[1],[2]	$ 0.97	[1],[2]
Discontinued operations (in dollars per share)			$ 0.01	[1],[2]
Net income (in dollars per share)	$ 0.95	[1],[2]	$ 0.99	[1],[2]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per common share (in shares)					36.6	9.7	21.0	25.5		8.8
Number of common stocks issued to convert equity units									5.9
Antidilutive securities weighted average exercise price (in dollars per share)					$ 60.68	$ 192.03	$ 178.50	$ 106.10		$ 318.30

[1] Earnings per share amounts 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 pershare on continuing operations and discontinued operations may not sum to earnings per share on net income.