CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Statements of Income and Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues
Dividends from subsidiaries		$ 0	$ 0	$ 0	$ 0
Interest revenue		13,314	19,177	45,042	57,965
Interest revenue—intercompany		0	0	0	0
Interest expense		2,821	7,536	11,977	22,615
Interest expense—intercompany		0	0	0	0
Net interest revenue		10,493	11,641	33,065	35,350
Commissions and fees		2,753	2,906	8,707	8,713
Commissions and fees—intercompany		0	0	0	0
Principal transactions		2,508	2,802	11,926	7,480
Principal transactions—intercompany		0	0	0	0
Other income		1,548	1,225	4,101	4,365
Other income—intercompany		0	0	0	0
Total non-interest revenues		6,809	6,933	24,734	20,558
Total revenues, net of interest expense		17,302	18,574	57,799	55,908
Total provisions for credit losses and for benefits and claims		2,262	2,088	17,192	6,161
Operating expenses
Compensation and benefits		5,595	5,329	16,873	16,368
Compensation and benefits—intercompany		0	0	0	0
Other operating		5,369	5,135	15,100	15,180
Other operating—intercompany		0	0	0	0
Total operating expenses		10,964	10,464	31,973	31,548
Equity in undistributed income of subsidiaries		0	0	0	0
Income (loss) from continuing operations before income taxes		4,076	6,022	8,634	18,199
Provision for income taxes		815	1,079	1,522	3,727
Income from continuing operations		3,261	4,943	7,112	14,472
Loss from discontinued operations, net of taxes		(7)	(15)	(26)	0
Net income before attribution of noncontrolling interests		3,254	4,928	7,086	14,472
Noncontrolling interests		24	15	18	50
Citigroup’s net income		3,230	4,913	7,068	14,422
Comprehensive income
Add: Other comprehensive income (loss)	[1]	280	(932)	3,253	1,035
Citigroup’s total comprehensive income		3,510	3,981	10,321	15,457
Add: Other comprehensive income (loss) attributable to noncontrolling interests		19	(33)	7	(26)
Add: Net income attributable to noncontrolling interests		24	15	18	50
Total comprehensive income (loss)		3,553	3,963	10,346	15,481
Reportable legal entities | Citigroup parent company
Revenues
Dividends from subsidiaries		2,250	4,829	2,355	19,045
Interest revenue		0	2	0	2
Interest revenue—intercompany		991	1,240	3,202	3,892
Interest expense		1,267	1,214	3,675	3,763
Interest expense—intercompany		61	246	451	760
Net interest revenue		(337)	(218)	(924)	(629)
Commissions and fees		0	0	0	0
Commissions and fees—intercompany		0	(19)	(19)	(20)
Principal transactions		(169)	(1,535)	(1,099)	(2,925)
Principal transactions—intercompany		42	284	606	1,522
Other income		(90)	1,213	(24)	1,164
Other income—intercompany		78	(95)	16	(120)
Total non-interest revenues		(139)	(152)	(520)	(379)
Total revenues, net of interest expense		1,774	4,459	911	18,037
Total provisions for credit losses and for benefits and claims		0	0	0	0
Operating expenses
Compensation and benefits		(21)	(6)	112	31
Compensation and benefits—intercompany		44	54	119	97
Other operating		5	(38)	37	(24)
Other operating—intercompany		4	6	12	16
Total operating expenses		32	16	280	120
Equity in undistributed income of subsidiaries		1,140	328	5,615	(4,021)
Income (loss) from continuing operations before income taxes		2,882	4,771	6,246	13,896
Provision for income taxes		(348)	(142)	(822)	(526)
Income from continuing operations		3,230	4,913	7,068	14,422
Loss from discontinued operations, net of taxes		0	0	0	0
Net income before attribution of noncontrolling interests		3,230	4,913	7,068	14,422
Noncontrolling interests		0	0	0	0
Citigroup’s net income		3,230	4,913	7,068	14,422
Comprehensive income
Add: Other comprehensive income (loss)		280	(932)	3,253	1,035
Citigroup’s total comprehensive income		3,510	3,981	10,321	15,457
Add: Other comprehensive income (loss) attributable to noncontrolling interests		0	0	0	0
Add: Net income attributable to noncontrolling interests		0	0	0	0
Total comprehensive income (loss)		3,510	3,981	10,321	15,457
Reportable legal entities | CGMHI
Revenues
Dividends from subsidiaries		0	0	0	0
Interest revenue		1,128	2,595	4,340	8,351
Interest revenue—intercompany		153	502	776	1,523
Interest expense		274	1,831	1,795	5,566
Interest expense—intercompany		416	1,088	1,819	3,315
Net interest revenue		591	178	1,502	993
Commissions and fees		1,494	1,296	4,815	3,912
Commissions and fees—intercompany		30	39	267	254
Principal transactions		(3,779)	291	(518)	399
Principal transactions—intercompany		4,350	693	4,849	2,054
Other income		208	67	468	664
Other income—intercompany		12	30	38	86
Total non-interest revenues		2,315	2,416	9,919	7,369
Total revenues, net of interest expense		2,906	2,594	11,421	8,362
Total provisions for credit losses and for benefits and claims		(1)	0	(1)	0
Operating expenses
Compensation and benefits		1,165	1,277	3,806	3,727
Compensation and benefits—intercompany		0	0	0	0
Other operating		597	571	1,789	1,664
Other operating—intercompany		772	625	1,629	1,789
Total operating expenses		2,534	2,473	7,224	7,180
Equity in undistributed income of subsidiaries		0	0	0	0
Income (loss) from continuing operations before income taxes		373	121	4,198	1,182
Provision for income taxes		165	12	1,217	160
Income from continuing operations		208	109	2,981	1,022
Loss from discontinued operations, net of taxes		0	0	0	0
Net income before attribution of noncontrolling interests		208	109	2,981	1,022
Noncontrolling interests		0	0	0	0
Citigroup’s net income		208	109	2,981	1,022
Comprehensive income
Add: Other comprehensive income (loss)		(51)	41	277	(260)
Citigroup’s total comprehensive income		157	150	3,258	762
Add: Other comprehensive income (loss) attributable to noncontrolling interests		0	0	0	0
Add: Net income attributable to noncontrolling interests		0	0	0	0
Total comprehensive income (loss)		157	150	3,258	762
Reportable legal entities | Other Citigroup subsidiaries and eliminations
Revenues
Dividends from subsidiaries		0	0	0	0
Interest revenue		12,186	16,580	40,702	49,612
Interest revenue—intercompany		(1,144)	(1,742)	(3,978)	(5,415)
Interest expense		1,280	4,491	6,507	13,286
Interest expense—intercompany		(477)	(1,334)	(2,270)	(4,075)
Net interest revenue		10,239	11,681	32,487	34,986
Commissions and fees		1,259	1,610	3,892	4,801
Commissions and fees—intercompany		(30)	(20)	(248)	(234)
Principal transactions		6,456	4,046	13,543	10,006
Principal transactions—intercompany		(4,392)	(977)	(5,455)	(3,576)
Other income		1,430	(55)	3,657	2,537
Other income—intercompany		(90)	65	(54)	34
Total non-interest revenues		4,633	4,669	15,335	13,568
Total revenues, net of interest expense		14,872	16,350	47,822	48,554
Total provisions for credit losses and for benefits and claims		2,263	2,088	17,193	6,161
Operating expenses
Compensation and benefits		4,451	4,058	12,955	12,610
Compensation and benefits—intercompany		(44)	(54)	(119)	(97)
Other operating		4,767	4,602	13,274	13,540
Other operating—intercompany		(776)	(631)	(1,641)	(1,805)
Total operating expenses		8,398	7,975	24,469	24,248
Equity in undistributed income of subsidiaries		0	0	0	0
Income (loss) from continuing operations before income taxes		4,211	6,287	6,160	18,145
Provision for income taxes		998	1,209	1,127	4,093
Income from continuing operations		3,213	5,078	5,033	14,052
Loss from discontinued operations, net of taxes		(7)	(15)	(26)	0
Net income before attribution of noncontrolling interests		3,206	5,063	5,007	14,052
Noncontrolling interests		24	15	18	50
Citigroup’s net income		3,182	5,048	4,989	14,002
Comprehensive income
Add: Other comprehensive income (loss)		(2,178)	2,895	10,058	4,628
Citigroup’s total comprehensive income		1,004	7,943	15,047	18,630
Add: Other comprehensive income (loss) attributable to noncontrolling interests		19	(33)	7	(26)
Add: Net income attributable to noncontrolling interests		24	15	18	50
Total comprehensive income (loss)		1,047	7,925	15,072	18,654
Consolidating adjustments
Revenues
Dividends from subsidiaries		(2,250)	(4,829)	(2,355)	(19,045)
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 income		0	0	0	0
Other income—intercompany		0	0	0	0
Total non-interest revenues		0	0	0	0
Total revenues, net of interest expense		(2,250)	(4,829)	(2,355)	(19,045)
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		(1,140)	(328)	(5,615)	4,021
Income (loss) from continuing operations before income taxes		(3,390)	(5,157)	(7,970)	(15,024)
Provision for income taxes		0	0	0	0
Income from continuing operations		(3,390)	(5,157)	(7,970)	(15,024)
Loss from discontinued operations, net of taxes		0	0	0	0
Net income before attribution of noncontrolling interests		(3,390)	(5,157)	(7,970)	(15,024)
Noncontrolling interests		0	0	0	0
Citigroup’s net income		(3,390)	(5,157)	(7,970)	(15,024)
Comprehensive income
Add: Other comprehensive income (loss)		2,229	(2,936)	(10,335)	(4,368)
Citigroup’s total comprehensive income		(1,161)	(8,093)	(18,305)	(19,392)
Add: Other comprehensive income (loss) attributable to noncontrolling interests		0	0	0	0
Add: Net income attributable to noncontrolling interests		0	0	0	0
Total comprehensive income (loss)		$ (1,161)	$ (8,093)	$ (18,305)	$ (19,392)

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