EARNINGS PER SHARE (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended				6 Months Ended
	Dec. 17, 2012	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
EARNINGS PER SHARE
Income from continuing operations before attribution of noncontrolling interests		$ 4,188		$ 2,979		$ 8,119		$ 6,024
Less: Noncontrolling interests from continuing operations		36		40		126		166
Net income from continuing operations (for EPS purposes)		4,152		2,939		7,993		5,858
Income (loss) from discontinued operations, net of taxes		30		7		(3)		19
Citigroup's net income		4,182		2,946		7,990		5,877
Less: Preferred dividends		9		9		13		13
Net income available to common shareholders		4,173		2,937		7,977		5,864
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares that contain nonforfeitable rights to dividends, applicable to basic EPS		83		69		155		123
Net income allocated to common shareholders for basic		4,090		2,868		7,822		5,741
Add: Interest expense, net of tax, and dividends on convertible securities and adjustment of undistributed earnings allocated to employee restricted and deferred shares with nonforfeitable rights to dividends, applicable to diluted EPS		1		4		1		8
Net income allocated to common shareholders for diluted EPS		$ 4,091		$ 2,872		$ 7,823		$ 5,749
Weighted-average common shares outstanding applicable to basic EPS		3,040,700,000		2,926,600,000		3,040,400,000		2,926,400,000
Effect of dilutive securities
T-DECs (in shares)				87,800,000				87,800,000
Options (in shares)		5,000,000				4,500,000
Other employee plans (in shares)		500,000		500,000		500,000		500,000
Convertible securities (in shares)		100,000		100,000		100,000		100,000
Adjusted weighted-average common shares outstanding applicable to diluted EPS		3,046,300,000		3,015,000,000		3,045,500,000		3,014,800,000
Basic earnings per share
Income from continuing operations (in dollars per share)		$ 1.34	[1]	$ 0.98	[1]	$ 2.57	[1]	$ 1.96	[1]
Discontinued operations (in dollars per share)		$ 0.01	[1]					$ 0.01	[1]
Net income (in dollars per share)		$ 1.35	[1]	$ 0.98	[1]	$ 2.57	[1]	$ 1.96	[1]
Diluted earnings per share
Income from continuing operations (in dollars per share)		$ 1.33	[1]	$ 0.95	[1]	$ 2.57	[1]	$ 1.90	[1]
Discontinued operations (in dollars per share)		$ 0.01	[1]					$ 0.01	[1]
Net income (in dollars per share)		$ 1.34	[1]	$ 0.95	[1]	$ 2.57	[1]	$ 1.91	[1]
Antidilutive Securities Excluded from Computation of Earnings Per Share
Number of shares delivered for the final settlement of the prepaid stock purchase contract	96,337,772
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)		8,200,000		35,800,000
Antidilutive securities exercise price (in dollars per share)		$ 79.80		$ 52.80		$ 79.80		$ 52.80
Warrants issued to U.S. Treasury as part of TARP and loss-sharing agreement | Warrant with the exercise price of $178.50
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per common share (in shares)		21,000,000		21,000,000
Antidilutive securities exercise price (in dollars per share)		$ 178.50		$ 178.50		$ 178.50		$ 178.50
Warrants issued to U.S. Treasury as part of TARP and loss-sharing agreement | Warrant with the exercise price of $106.10
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per common share (in shares)		25,500,000		25,500,000
Antidilutive securities exercise price (in dollars per share)		$ 106.10		$ 106.10		$ 106.10		$ 106.10

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