CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Statements of Income and Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues
Dividends from subsidiaries	$ 0	$ 0
Interest revenue	14,423	14,167
Interest revenue—intercompany	0	0
Interest expense	3,566	2,940
Interest expense—intercompany	0	0
Net interest revenue	10,857	11,227
Commissions and fees	2,759	2,463
Commissions and fees—intercompany	0	0
Principal transactions	3,022	1,840
Principal transactions—intercompany	0	0
Other income	1,482	2,025
Other income—intercompany	0	0
Total non-interest revenues	7,263	6,328
Total revenues, net of interest expense	18,120	17,555
Provisions for credit losses and for benefits and claims	1,662	2,045
Operating expenses
Compensation and benefits	5,534	5,556
Compensation and benefits—intercompany	0	0
Other operating	4,943	4,967
Other operating—intercompany	0	0
Total operating expenses	10,477	10,523
Equity in undistributed income of subsidiaries	0	0
Income (loss) from continuing operations before income taxes	5,981	4,987
Provision for income taxes	1,863	1,479
Income from continuing operations	4,118	3,508
Income (loss) from discontinued operations, net of taxes	(18)	(2)
Net income before attribution of noncontrolling interests	4,100	3,506
Noncontrolling interests	10	5
Citigroup’s net income	4,090	3,501
Comprehensive income
Add: Other comprehensive income	1,464	2,733
Citigroup’s total comprehensive income	5,554	6,234
Add: Other comprehensive income attributable to noncontrolling interests	31	27
Add: Net income attributable to noncontrolling interests	10	5
Total comprehensive income	5,595	6,266
Reportable legal entities | Citigroup parent company
Revenues
Dividends from subsidiaries	3,750	2,800
Interest revenue	1	2
Interest revenue—intercompany	793	872
Interest expense	1,218	1,070
Interest expense—intercompany	90	41
Net interest revenue	(514)	(237)
Commissions and fees	0	0
Commissions and fees—intercompany	0	(2)
Principal transactions	(163)	(209)
Principal transactions—intercompany	204	258
Other income	(39)	(3,094)
Other income—intercompany	(123)	3,260
Total non-interest revenues	(121)	213
Total revenues, net of interest expense	3,115	2,776
Provisions for credit losses and for benefits and claims	0	0
Operating expenses
Compensation and benefits	(14)	8
Compensation and benefits—intercompany	31	3
Other operating	28	267
Other operating—intercompany	(59)	1
Total operating expenses	(14)	279
Equity in undistributed income of subsidiaries	587	944
Income (loss) from continuing operations before income taxes	3,716	3,441
Provision for income taxes	(374)	(60)
Income from continuing operations	4,090	3,501
Income (loss) from discontinued operations, net of taxes	0	0
Net income before attribution of noncontrolling interests	4,090	3,501
Noncontrolling interests	0	0
Citigroup’s net income	4,090	3,501
Comprehensive income
Add: Other comprehensive income	1,464	2,733
Citigroup’s total comprehensive income	5,554	6,234
Add: Other comprehensive income attributable to noncontrolling interests	0	0
Add: Net income attributable to noncontrolling interests	0	0
Total comprehensive income	5,554	6,234
Reportable legal entities | CGMHI
Revenues
Dividends from subsidiaries	0	0
Interest revenue	1,027	1,146
Interest revenue—intercompany	157	136
Interest expense	396	364
Interest expense—intercompany	426	429
Net interest revenue	362	489
Commissions and fees	1,255	960
Commissions and fees—intercompany	2	(6)
Principal transactions	1,606	(137)
Principal transactions—intercompany	(682)	748
Other income	74	76
Other income—intercompany	34	(140)
Total non-interest revenues	2,289	1,501
Total revenues, net of interest expense	2,651	1,990
Provisions for credit losses and for benefits and claims	0	0
Operating expenses
Compensation and benefits	1,262	1,289
Compensation and benefits—intercompany	0	0
Other operating	406	386
Other operating—intercompany	468	307
Total operating expenses	2,136	1,982
Equity in undistributed income of subsidiaries	0	0
Income (loss) from continuing operations before income taxes	515	8
Provision for income taxes	215	37
Income from continuing operations	300	(29)
Income (loss) from discontinued operations, net of taxes	0	0
Net income before attribution of noncontrolling interests	300	(29)
Noncontrolling interests	0	2
Citigroup’s net income	300	(31)
Comprehensive income
Add: Other comprehensive income	(20)	47
Citigroup’s total comprehensive income	280	16
Add: Other comprehensive income attributable to noncontrolling interests	0	0
Add: Net income attributable to noncontrolling interests	0	2
Total comprehensive income	280	18
Reportable legal entities | Other Citigroup subsidiaries and eliminations
Revenues
Dividends from subsidiaries	0	0
Interest revenue	13,395	13,019
Interest revenue—intercompany	(950)	(1,008)
Interest expense	1,952	1,506
Interest expense—intercompany	(516)	(470)
Net interest revenue	11,009	10,975
Commissions and fees	1,504	1,503
Commissions and fees—intercompany	(2)	8
Principal transactions	1,579	2,186
Principal transactions—intercompany	478	(1,006)
Other income	1,447	5,043
Other income—intercompany	89	(3,120)
Total non-interest revenues	5,095	4,614
Total revenues, net of interest expense	16,104	15,589
Provisions for credit losses and for benefits and claims	1,662	2,045
Operating expenses
Compensation and benefits	4,286	4,259
Compensation and benefits—intercompany	(31)	(3)
Other operating	4,509	4,314
Other operating—intercompany	(409)	(308)
Total operating expenses	8,355	8,262
Equity in undistributed income of subsidiaries	0	0
Income (loss) from continuing operations before income taxes	6,087	5,282
Provision for income taxes	2,022	1,502
Income from continuing operations	4,065	3,780
Income (loss) from discontinued operations, net of taxes	(18)	(2)
Net income before attribution of noncontrolling interests	4,047	3,778
Noncontrolling interests	10	3
Citigroup’s net income	4,037	3,775
Comprehensive income
Add: Other comprehensive income	(3,721)	(534)
Citigroup’s total comprehensive income	316	3,241
Add: Other comprehensive income attributable to noncontrolling interests	31	27
Add: Net income attributable to noncontrolling interests	10	3
Total comprehensive income	357	3,271
Consolidating adjustments
Revenues
Dividends from subsidiaries	(3,750)	(2,800)
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 income	0	0
Other income—intercompany	0	0
Total non-interest revenues	0	0
Total revenues, net of interest expense	(3,750)	(2,800)
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	(587)	(944)
Income (loss) from continuing operations before income taxes	(4,337)	(3,744)
Provision for income taxes	0	0
Income from continuing operations	(4,337)	(3,744)
Income (loss) from discontinued operations, net of taxes	0	0
Net income before attribution of noncontrolling interests	(4,337)	(3,744)
Noncontrolling interests	0	0
Citigroup’s net income	(4,337)	(3,744)
Comprehensive income
Add: Other comprehensive income	3,741	487
Citigroup’s total comprehensive income	(596)	(3,257)
Add: Other comprehensive income attributable to noncontrolling interests	0	0
Add: Net income attributable to noncontrolling interests	0	0
Total comprehensive income	$ (596)	$ (3,257)