OPERATING SEGMENTS (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021 USD ($) country	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($) country		Dec. 31, 2020 USD ($)		Dec. 31, 2019 USD ($)
Segment reporting information
Revenues, net of interest expense	$ 17,017	$ 17,447	$ 17,753	$ 19,667	$ 16,832	$ 17,677	$ 20,036	$ 20,956	$ 71,884		$ 75,501		$ 75,067
Provision (benefits) for income taxes	771	1,193	1,155	2,332	1,116	777	52	580	5,451		2,525		4,430
Income (loss) from continuing operations	3,179	4,669	6,193	7,977	4,325	3,177	1,057	2,548	22,018		11,107		19,471
Identifiable assets	2,291,413				2,260,090				2,291,413		2,260,090
Provisions for credit losses and for benefits and claims	(465)	$ (192)	$ (1,066)	$ (2,055)	(46)	$ 2,384	$ 8,197	$ 6,960	(3,778)	[1]	17,495	[1]	8,383	[1]
Total Citicorp and Corporate/Other
Segment reporting information
Revenues, net of interest expense									71,884		75,501		75,067
Provision (benefits) for income taxes									5,451		2,525		4,430
Income (loss) from continuing operations									22,018		11,107		19,471
Identifiable assets	$ 2,291,000				2,260,000				2,291,000		2,260,000
Operating Segments | Citicorp | North America
Segment reporting information
Revenues, net of interest expense									34,200		36,800		34,100
Operating Segments | Citicorp | EMEA
Segment reporting information
Revenues, net of interest expense									13,100		13,000		12,200
Operating Segments | Citicorp | Latin America
Segment reporting information
Revenues, net of interest expense									9,200		9,400		10,600
Operating Segments | Citicorp | Asia
Segment reporting information
Revenues, net of interest expense									$ 14,700		16,200		16,200
Operating Segments | Institutional Clients Group
Segment reporting information
Number of countries where the entity provides a broad range of banking and financial products and services (over) | country	95								95
Revenues, net of interest expense									$ 43,887		45,088		39,824
Provision (benefits) for income taxes									4,524		3,303		3,524
Income (loss) from continuing operations									15,763		11,553		12,776
Identifiable assets	$ 1,762,000				1,730,000				1,762,000		1,730,000
Provisions for credit losses and for benefits and claims									(2,900)		5,600		600
Operating Segments | Global Consumer Banking
Segment reporting information
Revenues, net of interest expense									27,330		30,342		33,221
Provision (benefits) for income taxes									1,745		143		1,708
Income (loss) from continuing operations									6,046		663		5,579
Identifiable assets	432,000				434,000				432,000		434,000
Provisions for credit losses and for benefits and claims									(500)		11,700		7,900
Corporate/Other
Segment reporting information
Revenues, net of interest expense									667		71		2,022
Provision (benefits) for income taxes									(818)		(921)		(802)
Income (loss) from continuing operations									209		(1,109)		1,116
Identifiable assets	$ 97,000				$ 96,000				97,000		96,000
Provisions for credit losses and for benefits and claims									$ (400)		$ 200		$ (100)

[1] This total excludes the provision for credit losses on AFS securities, which is disclosed separately above.