EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share
Income from continuing operations before attribution of noncontrolling interests		$ 3,263		$ 2,952	$ 6,671	$ 7,604
Noncontrolling interests		46		36	82	81
Net income from continuing operations (for EPS purposes)		3,217		2,916	6,589	7,523
Income (loss) from discontinued operations, net of taxes		0		(1)	(1)	(2)
Citigroup’s net income		3,217		2,915	6,588	7,521
Less: Preferred dividends		242		288	521	565
Net income available to common shareholders		2,975		2,627	6,067	6,956
Less: Dividends and undistributed earnings allocated to employee restricted and deferred shares with rights to dividends, and other relevant items, applicable to basic EPS		32		33	77	68
Net income allocated to common shareholders for basic EPS		$ 2,943		$ 2,594	$ 5,990	$ 6,888
Weighted-average common shares outstanding applicable to basic EPS (in shares)		1,907.7		1,942.8	1,909.1	1,943.2
Basic earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 1.54		$ 1.34	$ 3.14	$ 3.55
Discontinued operations (in dollars per share)	[1]	0		0	0	0
Net income (in dollars per share)	[1]	$ 1.54		$ 1.34	$ 3.14	$ 3.54
Add back: Dividends allocated to employee restricted and deferred shares with rights to dividends that are forfeitable		$ 19		$ 15	$ 34	$ 26
Net income allocated to common shareholders for diluted EPS		$ 2,962		$ 2,609	$ 6,024	$ 6,914
Effect of dilutive securities
Other employee plans (in shares)		38.0		25.8	35.3	23.1
Adjusted weighted-average common shares outstanding applicable to diluted EPS (in shares)		1,945.7		1,968.6	1,944.4	1,966.3
Diluted earnings per share
Income from continuing operations (in dollars per share)	[1]	$ 1.52		$ 1.33	$ 3.10	$ 3.52
Discontinued operations (in dollars per share)	[1]	0		0	0	0
Net income (in dollars per share)	[1]	$ 1.52		$ 1.33	$ 3.10	$ 3.52
Excise tax		$ 14
Income allocated to employees with no rights to dividends		38
Series D
Diluted earnings per share
Issuance costs		$ 8
Series J
Diluted earnings per share
Issuance costs			$ 12

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