EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Income from continuing operations before attribution to noncontrolling interests		$ 4,789	$ 6,193	$ 9,114	$ 14,170
Noncontrolling interests		21	10	38	43
Net income from continuing operations (for EPS purposes)		4,768	6,183	9,076	14,127
Income (loss) from discontinued operations, net of taxes		(221)	10	(223)	8
Citigroup’s net income		4,547	6,193	8,853	14,135
Less: Preferred dividends		238	253	517	545
Net income available to common shareholders		4,309	5,940	8,336	13,590
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares with rights to dividends, applicable to basic EPS		35	41	60	107
Net income allocated to common shareholders for basic EPS		$ 4,274	$ 5,899	$ 8,276	$ 13,483
Weighted-average common shares outstanding applicable to basic EPS (in shares)		1,941.5	2,056.5	1,956.6	2,069.3
Basic earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 2.32	$ 2.86	$ 4.34	$ 6.51
Discontinued operations (in dollars per share)	[1]	(0.11)	0	(0.11)	0
Net income (in dollars per share)	[1]	$ 2.20	$ 2.87	$ 4.23	$ 6.52
Add back: Dividends allocated to employee restricted and deferred shares with rights to dividends that are forfeitable		$ 11	$ 8	$ 19	$ 15
Net income allocated to common shareholders for diluted EPS		$ 4,285	$ 5,907	$ 8,295	$ 13,498
Effect of dilutive securities
Options (in shares)		0.0	0.0	0.0	0.0
Other employee plans (in shares)		16.6	16.5	16.6	15.5
Adjusted weighted-average common shares outstanding applicable to diluted EPS (in shares)		1,958.1	2,073.0	1,973.2	2,084.8
Diluted earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 2.30	$ 2.84	$ 4.32	$ 6.47
Discontinued operations (in dollars per share)	[1]	(0.11)	0	(0.11)	0
Net income (in dollars per share)	[1]	$ 2.19	$ 2.85	$ 4.20	$ 6.47

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