EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Earnings Per Share [Abstract]
Income from continuing operations before attribution of noncontrolling interests	$ 4,817		3,952
Less: Noncontrolling interests from continuing operations	42		45
Net income from continuing operations (for EPS purposes)	4,775		3,907
Income (loss) from discontinued operations, net of taxes	(5)		37
Citigroup’s net income	4,770		3,944
Less: Preferred dividends	128		124
Net income available to common shareholders	4,642		3,820
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares with nonforfeitable rights to dividends, applicable to basic EPS	62		62
Net income allocated to common shareholders for basic EPS	4,580		3,758
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	0		0
Net income allocated to common shareholders for diluted EPS	$ 4,580		3,758
Weighted-average common shares outstanding applicable to basic EPS	3,034.2		3,037.4
Effect of dilutive securities
Options (in shares)	4.9		5.6
Other employee plans (in shares)	0.2		0.3
Convertible securities (in shares)	0		0
Adjusted weighted-average common shares outstanding applicable to diluted EPS	3,039.3		3,043.3
Basic earnings per share
Income from continuing operations (in dollars per share)	$ 1.51	[1]	1.23	[1]
Discontinued operations (in dollars per share)	$ 0.00	[1]	0.01	[1]
Net income (in dollars per share)	$ 1.51	[1]	1.24	[1]
Diluted earnings per share
Income from continuing operations (in dollars per share)	$ 1.51	[1]	1.22	[1]
Discontinued operations (in dollars per share)	$ 0.00	[1]	0.01	[1]
Net income (in dollars per share)	$ 1.51	[1]	1.23	[1]
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)	0.9		0.9
Antidilutive securities exercise price (in dollars per share)	$ 195.47		194.37
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)	21.0		21.0
Antidilutive securities exercise price (in dollars per share)	$ 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)	25.5		25.5
Antidilutive securities exercise price (in dollars per share)	$ 106.10				$ 106.10

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