CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Statements of Income and Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Revenues
Dividends from subsidiaries		$ 0	$ 0
Interest revenue		12,534	17,139
Interest revenue—intercompany		0	0
Interest expense		2,368	5,647
Interest expense—intercompany		0	0
Net interest revenue		10,166	11,492
Commissions and fees		3,670	3,021
Commissions and fees—intercompany		0	0
Principal transactions		3,913	5,261
Principal transactions—intercompany		0	0
Other revenue		1,578	957
Other revenue—intercompany		0	0
Total non-interest revenues		9,161	9,239
Total revenues, net of interest expense		19,327	20,731
Total provisions for credit losses and for benefits and claims		(2,055)	6,960
Operating expenses
Compensation and benefits		6,001	5,654
Compensation and benefits—intercompany		0	0
Other operating		5,072	4,989
Other operating—intercompany		0	0
Total operating expenses		11,073	10,643
Equity in undistributed income of subsidiaries		0	0
Income (loss) from continuing operations before income taxes		10,309	3,128
Provision for income taxes		2,332	580
Income from continuing operations		7,977	2,548
Loss from discontinued operations, net of taxes		(2)	(18)
Net income before attribution of noncontrolling interests		7,975	2,530
Noncontrolling interests		33	(6)
Citigroup’s net income		7,942	2,536
Comprehensive income
Add: Other comprehensive income (loss)	[1]	(2,953)	3,797
Citigroup’s total comprehensive income		4,989	6,333
Add: Other comprehensive loss attributable to noncontrolling interests		(58)	(51)
Add: Net income (loss) attributable to noncontrolling interests		33	(6)
Total comprehensive income (loss)		4,964	6,276
Reportable legal entities | Citigroup parent company
Revenues
Dividends from subsidiaries		100	105
Interest revenue		0	0
Interest revenue—intercompany		958	1,144
Interest expense		1,212	1,143
Interest expense—intercompany		84	248
Net interest revenue		(338)	(247)
Commissions and fees		0	0
Commissions and fees—intercompany		(26)	(19)
Principal transactions		1,769	(672)
Principal transactions—intercompany		(1,878)	502
Other revenue		55	80
Other revenue—intercompany		(64)	(70)
Total non-interest revenues		(144)	(179)
Total revenues, net of interest expense		(382)	(321)
Total provisions for credit losses and for benefits and claims		0	0
Operating expenses
Compensation and benefits		28	28
Compensation and benefits—intercompany		24	74
Other operating		11	23
Other operating—intercompany		3	4
Total operating expenses		66	129
Equity in undistributed income of subsidiaries		8,173	2,382
Income (loss) from continuing operations before income taxes		7,725	1,932
Provision for income taxes		(217)	(604)
Income from continuing operations		7,942	2,536
Loss from discontinued operations, net of taxes		0	0
Net income before attribution of noncontrolling interests		7,942	2,536
Noncontrolling interests		0	0
Citigroup’s net income		7,942	2,536
Comprehensive income
Add: Other comprehensive income (loss)		(2,953)	3,797
Citigroup’s total comprehensive income		4,989	6,333
Add: Other comprehensive loss attributable to noncontrolling interests		0	0
Add: Net income (loss) attributable to noncontrolling interests		0	0
Total comprehensive income (loss)		4,989	6,333
Reportable legal entities | CGMHI
Revenues
Dividends from subsidiaries		0	0
Interest revenue		971	1,903
Interest revenue—intercompany		145	341
Interest expense		223	1,141
Interest expense—intercompany		329	782
Net interest revenue		564	321
Commissions and fees		2,161	1,550
Commissions and fees—intercompany		47	164
Principal transactions		5,658	6,254
Principal transactions—intercompany		(4,238)	(4,391)
Other revenue		103	49
Other revenue—intercompany		(20)	13
Total non-interest revenues		3,711	3,639
Total revenues, net of interest expense		4,275	3,960
Total provisions for credit losses and for benefits and claims		4	(1)
Operating expenses
Compensation and benefits		1,334	1,296
Compensation and benefits—intercompany		0	0
Other operating		642	598
Other operating—intercompany		680	482
Total operating expenses		2,656	2,376
Equity in undistributed income of subsidiaries		0	0
Income (loss) from continuing operations before income taxes		1,615	1,585
Provision for income taxes		452	337
Income from continuing operations		1,163	1,248
Loss from discontinued operations, net of taxes		0	0
Net income before attribution of noncontrolling interests		1,163	1,248
Noncontrolling interests		0	0
Citigroup’s net income		1,163	1,248
Comprehensive income
Add: Other comprehensive income (loss)		(50)	1,757
Citigroup’s total comprehensive income		1,113	3,005
Add: Other comprehensive loss attributable to noncontrolling interests		0	0
Add: Net income (loss) attributable to noncontrolling interests		0	0
Total comprehensive income (loss)		1,113	3,005
Reportable legal entities | Other Citigroup subsidiaries and eliminations
Revenues
Dividends from subsidiaries		0	0
Interest revenue		11,563	15,236
Interest revenue—intercompany		(1,103)	(1,485)
Interest expense		933	3,363
Interest expense—intercompany		(413)	(1,030)
Net interest revenue		9,940	11,418
Commissions and fees		1,509	1,471
Commissions and fees—intercompany		(21)	(145)
Principal transactions		(3,514)	(321)
Principal transactions—intercompany		6,116	3,889
Other revenue		1,420	828
Other revenue—intercompany		84	57
Total non-interest revenues		5,594	5,779
Total revenues, net of interest expense		15,534	17,197
Total provisions for credit losses and for benefits and claims		(2,059)	6,961
Operating expenses
Compensation and benefits		4,639	4,330
Compensation and benefits—intercompany		(24)	(74)
Other operating		4,419	4,368
Other operating—intercompany		(683)	(486)
Total operating expenses		8,351	8,138
Equity in undistributed income of subsidiaries		0	0
Income (loss) from continuing operations before income taxes		9,242	2,098
Provision for income taxes		2,097	847
Income from continuing operations		7,145	1,251
Loss from discontinued operations, net of taxes		(2)	(18)
Net income before attribution of noncontrolling interests		7,143	1,233
Noncontrolling interests		33	(6)
Citigroup’s net income		7,110	1,239
Comprehensive income
Add: Other comprehensive income (loss)		537	13,459
Citigroup’s total comprehensive income		7,647	14,698
Add: Other comprehensive loss attributable to noncontrolling interests		(58)	(51)
Add: Net income (loss) attributable to noncontrolling interests		33	(6)
Total comprehensive income (loss)		7,622	14,641
Consolidating adjustments
Revenues
Dividends from subsidiaries		(100)	(105)
Interest revenue		0	0
Interest revenue—intercompany		0	0
Interest expense		0	0
Interest expense—intercompany		0	0
Net interest revenue		0	0
Commissions and fees		0	0
Commissions and fees—intercompany		0	0
Principal transactions		0	0
Principal transactions—intercompany		0	0
Other revenue		0	0
Other revenue—intercompany		0	0
Total non-interest revenues		0	0
Total revenues, net of interest expense		(100)	(105)
Total provisions for credit losses and for benefits and claims		0	0
Operating expenses
Compensation and benefits		0	0
Compensation and benefits—intercompany		0	0
Other operating		0	0
Other operating—intercompany		0	0
Total operating expenses		0	0
Equity in undistributed income of subsidiaries		(8,173)	(2,382)
Income (loss) from continuing operations before income taxes		(8,273)	(2,487)
Provision for income taxes		0	0
Income from continuing operations		(8,273)	(2,487)
Loss from discontinued operations, net of taxes		0	0
Net income before attribution of noncontrolling interests		(8,273)	(2,487)
Noncontrolling interests		0	0
Citigroup’s net income		(8,273)	(2,487)
Comprehensive income
Add: Other comprehensive income (loss)		(487)	(15,216)
Citigroup’s total comprehensive income		(8,760)	(17,703)
Add: Other comprehensive loss attributable to noncontrolling interests		0	0
Add: Net income (loss) attributable to noncontrolling interests		0	0
Total comprehensive income (loss)		$ (8,760)	$ (17,703)

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