EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share
Income from continuing operations before attribution of noncontrolling interests		$ 3,585	$ 3,515	$ 11,189	$ 12,629
Noncontrolling interests		41	30	122	68
Net income from continuing operations (for EPS purposes)		3,544	3,485	11,067	12,561
Income (loss) from discontinued operations, net of taxes		2	(6)	0	(229)
Citigroup’s net income		3,546	3,479	11,067	12,332
Less: Preferred dividends		333	277	898	794
Net income available to common shareholders		3,213	3,202	10,169	11,538
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares with rights to dividends, and other relevant items(1), applicable to basic EPS		53	28	121	89
Net income allocated to common shareholders for basic EPS		$ 3,160	$ 3,174	$ 10,048	$ 11,449
Weighted-average common shares outstanding applicable to basic EPS (in shares)		1,924.4	1,936.8	1,936.9	1,950.0
Basic earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 1.64	$ 1.64	$ 5.19	$ 5.99
Discontinued operations (in dollars per share)	[1]	0	0	0	(0.12)
Net income (in dollars per share)	[1]	$ 1.64	$ 1.64	$ 5.19	$ 5.87
Add back: Dividends allocated to employee restricted and deferred shares with rights to dividends that are forfeitable		$ 16	$ 11	$ 42	$ 30
Net income allocated to common shareholders for diluted EPS		$ 3,176	$ 3,185	$ 10,090	$ 11,479
Effect of dilutive securities
Options (in shares)		0.0	0.0	0.0	0.0
Other employee plans (in shares)		27.3	18.3	24.6	17.1
Adjusted weighted-average common shares outstanding applicable to diluted EPS (in shares)		1,951.7	1,955.1	1,961.5	1,967.1
Diluted earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 1.63	$ 1.63	$ 5.14	$ 5.95
Discontinued operations (in dollars per share)	[1]	0	0	0	(0.12)
Net income (in dollars per share)	[1]	$ 1.63	$ 1.63	$ 5.14	$ 5.84
Series A Preferred Stock and Series B Preferred Stock
Diluted earnings per share
Issuance costs		$ 16

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