EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Earnings Per Share [Abstract]
Income from continuing operations before attribution of noncontrolling interests		$ 2,952	$ 4,789	$ 7,604	$ 9,114
Noncontrolling interests		36	21	81	38
Net income from continuing operations (for EPS purposes)		2,916	4,768	7,523	9,076
Income (loss) from discontinued operations, net of taxes		(1)	(221)	(2)	(223)
Citigroup’s net income		2,915	4,547	7,521	8,853
Less: Preferred dividends		288	238	565	517
Net income available to common shareholders		2,627	4,309	6,956	8,336
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares with rights to dividends, applicable to basic EPS		33	35	68	60
Net income allocated to common shareholders for basic EPS		$ 2,594	$ 4,274	$ 6,888	$ 8,276
Weighted-average common shares outstanding applicable to basic EPS (in shares)		1,942.8	1,941.5	1,943.2	1,956.6
Basic earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 1.34	$ 2.32	$ 3.55	$ 4.34
Discontinued operations (in dollars per share)	[1]	0	(0.11)	0	(0.11)
Net income (in dollars per share)	[1]	$ 1.34	$ 2.20	$ 3.54	$ 4.23
Add back: Dividends allocated to employee restricted and deferred shares with rights to dividends that are forfeitable		$ 15	$ 11	$ 26	$ 19
Net income allocated to common shareholders for diluted EPS		$ 2,609	$ 4,285	$ 6,914	$ 8,295
Effect of dilutive securities
Options (in shares)		0.0	0.0	0.0	0.0
Other employee plans (in shares)		25.8	16.6	23.1	16.6
Adjusted weighted-average common shares outstanding applicable to diluted EPS (in shares)		1,968.6	1,958.1	1,966.3	1,973.2
Diluted earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 1.33	$ 2.30	$ 3.52	$ 4.32
Discontinued operations (in dollars per share)	[1]	0	(0.11)	0	(0.11)
Net income (in dollars per share)	[1]	$ 1.33	$ 2.19	$ 3.52	$ 4.20

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