CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Statements of Income and Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues
Dividends from subsidiaries		$ 0	$ 0	$ 0	$ 0
Interest revenue		12,463	14,589	24,997	31,728
Interest revenue—intercompany		0	0	0	0
Interest expense		2,264	3,509	4,632	9,156
Interest expense—intercompany		0	0	0	0
Net interest revenue		10,199	11,080	20,365	22,572
Commissions and fees		3,374	2,933	7,044	5,954
Commissions and fees—intercompany		0	0	0	0
Principal transactions		2,304	4,157	6,217	9,418
Principal transactions—intercompany		0	0	0	0
Other revenue		1,597	1,596	3,175	2,553
Other revenue—intercompany		0	0	0	0
Total non-interest revenues		7,275	8,686	16,436	17,925
Total revenues, net of interest expense		17,474	19,766	36,801	40,497
Total provisions for credit losses and for benefits and claims	[1]	(1,066)	8,197	(3,121)	15,157
Operating expenses
Compensation and benefits		5,982	5,624	11,983	11,278
Compensation and benefits—intercompany		0	0	0	0
Other operating		5,210	4,836	10,282	9,825
Other operating—intercompany		0	0	0	0
Total operating expenses		11,192	10,460	22,265	21,103
Equity in undistributed income of subsidiaries		0	0	0	0
Income (loss) from continuing operations before income taxes		7,348	1,109	17,657	4,237
Provision (benefits) for income taxes		1,155	52	3,487	632
Income (loss) from continuing operations		6,193	1,057	14,170	3,605
Income (loss) from discontinued operations, net of taxes		10	(1)	8	(19)
Net income (loss) before attribution of noncontrolling interests		6,203	1,056	14,178	3,586
Noncontrolling interests		10	0	43	(6)
Citigroup’s net income		6,193	1,056	14,135	3,592
Comprehensive income
Add: Other comprehensive income (loss)	[2]	(109)	(824)	(3,062)	2,973
Total Citigroup comprehensive income (loss)		6,084	232	11,073	6,565
Add: Other comprehensive income (loss) attributable to noncontrolling interests		18	39	(40)	(12)
Add: Net income (loss) attributable to noncontrolling interests		10	0	43	(6)
Total comprehensive income (loss)		6,112	271	11,076	6,547
Reportable legal entities | Citigroup parent company
Revenues
Dividends from subsidiaries		3,700	0	3,800	105
Interest revenue		0	0	0	0
Interest revenue—intercompany		954	1,067	1,912	2,211
Interest expense		1,209	1,265	2,421	2,408
Interest expense—intercompany		94	142	178	390
Net interest revenue		(349)	(340)	(687)	(587)
Commissions and fees		0	0	0	0
Commissions and fees—intercompany		(1)	0	(27)	(19)
Principal transactions		(892)	(258)	877	(930)
Principal transactions—intercompany		910	62	(968)	564
Other revenue		(4)	(14)	51	66
Other revenue—intercompany		3	8	(61)	(62)
Total non-interest revenues		16	(202)	(128)	(381)
Total revenues, net of interest expense		3,367	(542)	2,985	(863)
Total provisions for credit losses and for benefits and claims		2	0	2	0
Operating expenses
Compensation and benefits		0	105	28	133
Compensation and benefits—intercompany		24	1	48	75
Other operating		14	9	25	32
Other operating—intercompany		3	4	6	8
Total operating expenses		41	119	107	248
Equity in undistributed income of subsidiaries		2,567	1,847	10,740	4,229
Income (loss) from continuing operations before income taxes		5,891	1,186	13,616	3,118
Provision (benefits) for income taxes		(302)	130	(519)	(474)
Income (loss) from continuing operations		6,193	1,056	14,135	3,592
Income (loss) from discontinued operations, net of taxes		0	0	0	0
Net income (loss) before attribution of noncontrolling interests		6,193	1,056	14,135	3,592
Noncontrolling interests		0	0	0	0
Citigroup’s net income		6,193	1,056	14,135	3,592
Comprehensive income
Add: Other comprehensive income (loss)		(109)	(824)	(3,062)	2,973
Total Citigroup comprehensive income (loss)		6,084	232	11,073	6,565
Add: Other comprehensive income (loss) attributable to noncontrolling interests		0	0	0	0
Add: Net income (loss) attributable to noncontrolling interests		0	0	0	0
Total comprehensive income (loss)		6,084	232	11,073	6,565
Reportable legal entities | CGMHI
Revenues
Dividends from subsidiaries		0	0	0	0
Interest revenue		1,014	1,309	1,985	3,212
Interest revenue—intercompany		136	282	281	623
Interest expense		221	380	444	1,521
Interest expense—intercompany		330	621	659	1,403
Net interest revenue		599	590	1,163	911
Commissions and fees		1,836	1,771	3,997	3,321
Commissions and fees—intercompany		88	73	135	237
Principal transactions		919	(2,993)	6,577	3,261
Principal transactions—intercompany		(110)	4,890	(4,348)	499
Other revenue		139	211	242	260
Other revenue—intercompany		(8)	13	(28)	26
Total non-interest revenues		2,864	3,965	6,575	7,604
Total revenues, net of interest expense		3,463	4,555	7,738	8,515
Total provisions for credit losses and for benefits and claims		3	1	7	0
Operating expenses
Compensation and benefits		1,303	1,345	2,637	2,641
Compensation and benefits—intercompany		0	0	0	0
Other operating		680	594	1,322	1,192
Other operating—intercompany		808	375	1,488	857
Total operating expenses		2,791	2,314	5,447	4,690
Equity in undistributed income of subsidiaries		0	0	0	0
Income (loss) from continuing operations before income taxes		669	2,240	2,284	3,825
Provision (benefits) for income taxes		(119)	715	333	1,052
Income (loss) from continuing operations		788	1,525	1,951	2,773
Income (loss) from discontinued operations, net of taxes		0	0	0	0
Net income (loss) before attribution of noncontrolling interests		788	1,525	1,951	2,773
Noncontrolling interests		0	0	0	0
Citigroup’s net income		788	1,525	1,951	2,773
Comprehensive income
Add: Other comprehensive income (loss)		7	(1,429)	(43)	328
Total Citigroup comprehensive income (loss)		795	96	1,908	3,101
Add: Other comprehensive income (loss) attributable to noncontrolling interests		0	0	0	0
Add: Net income (loss) attributable to noncontrolling interests		0	0	0	0
Total comprehensive income (loss)		795	96	1,908	3,101
Reportable legal entities | Other Citigroup subsidiaries and eliminations
Revenues
Dividends from subsidiaries		0	0	0	0
Interest revenue		11,449	13,280	23,012	28,516
Interest revenue—intercompany		(1,090)	(1,349)	(2,193)	(2,834)
Interest expense		834	1,864	1,767	5,227
Interest expense—intercompany		(424)	(763)	(837)	(1,793)
Net interest revenue		9,949	10,830	19,889	22,248
Commissions and fees		1,538	1,162	3,047	2,633
Commissions and fees—intercompany		(87)	(73)	(108)	(218)
Principal transactions		2,277	7,408	(1,237)	7,087
Principal transactions—intercompany		(800)	(4,952)	5,316	(1,063)
Other revenue		1,462	1,399	2,882	2,227
Other revenue—intercompany		5	(21)	89	36
Total non-interest revenues		4,395	4,923	9,989	10,702
Total revenues, net of interest expense		14,344	15,753	29,878	32,950
Total provisions for credit losses and for benefits and claims		(1,071)	8,196	(3,130)	15,157
Operating expenses
Compensation and benefits		4,679	4,174	9,318	8,504
Compensation and benefits—intercompany		(24)	(1)	(48)	(75)
Other operating		4,516	4,233	8,935	8,601
Other operating—intercompany		(811)	(379)	(1,494)	(865)
Total operating expenses		8,360	8,027	16,711	16,165
Equity in undistributed income of subsidiaries		0	0	0	0
Income (loss) from continuing operations before income taxes		7,055	(470)	16,297	1,628
Provision (benefits) for income taxes		1,576	(793)	3,673	54
Income (loss) from continuing operations		5,479	323	12,624	1,574
Income (loss) from discontinued operations, net of taxes		10	(1)	8	(19)
Net income (loss) before attribution of noncontrolling interests		5,489	322	12,632	1,555
Noncontrolling interests		10	0	43	(6)
Citigroup’s net income		5,479	322	12,589	1,561
Comprehensive income
Add: Other comprehensive income (loss)		(1,966)	(1,223)	(1,429)	12,236
Total Citigroup comprehensive income (loss)		3,513	(901)	11,160	13,797
Add: Other comprehensive income (loss) attributable to noncontrolling interests		18	39	(40)	(12)
Add: Net income (loss) attributable to noncontrolling interests		10	0	43	(6)
Total comprehensive income (loss)		3,541	(862)	11,163	13,779
Consolidating adjustments
Revenues
Dividends from subsidiaries		(3,700)	0	(3,800)	(105)
Interest revenue		0	0	0	0
Interest revenue—intercompany		0	0	0	0
Interest expense		0	0	0	0
Interest expense—intercompany		0	0	0	0
Net interest revenue		0	0	0	0
Commissions and fees		0	0	0	0
Commissions and fees—intercompany		0	0	0	0
Principal transactions		0	0	0	0
Principal transactions—intercompany		0	0	0	0
Other revenue		0	0	0	0
Other revenue—intercompany		0	0	0	0
Total non-interest revenues		0	0	0	0
Total revenues, net of interest expense		(3,700)	0	(3,800)	(105)
Total provisions for credit losses and for benefits and claims		0	0	0	0
Operating expenses
Compensation and benefits		0	0	0	0
Compensation and benefits—intercompany		0	0	0	0
Other operating		0	0	0	0
Other operating—intercompany		0	0	0	0
Total operating expenses		0	0	0	0
Equity in undistributed income of subsidiaries		(2,567)	(1,847)	(10,740)	(4,229)
Income (loss) from continuing operations before income taxes		(6,267)	(1,847)	(14,540)	(4,334)
Provision (benefits) for income taxes		0	0	0	0
Income (loss) from continuing operations		(6,267)	(1,847)	(14,540)	(4,334)
Income (loss) from discontinued operations, net of taxes		0	0	0	0
Net income (loss) before attribution of noncontrolling interests		(6,267)	(1,847)	(14,540)	(4,334)
Noncontrolling interests		0	0	0	0
Citigroup’s net income		(6,267)	(1,847)	(14,540)	(4,334)
Comprehensive income
Add: Other comprehensive income (loss)		1,959	2,652	1,472	(12,564)
Total Citigroup comprehensive income (loss)		(4,308)	805	(13,068)	(16,898)
Add: Other comprehensive income (loss) attributable to noncontrolling interests		0	0	0	0
Add: Net income (loss) attributable to noncontrolling interests		0	0	0	0
Total comprehensive income (loss)		$ (4,308)	$ 805	$ (13,068)	$ (16,898)

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

[2] See Note 17 to the Consolidated Financial Statements.