CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Statements of Income and Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues
Dividends from subsidiaries	$ 0	$ 0	$ 0	$ 0
Interest revenue	14,653	14,714	43,176	44,187
Interest revenue—intercompany	0	0	0	0
Interest expense	3,174	2,941	9,234	9,020
Interest expense—intercompany	0	0	0	0
Net interest revenue	11,479	11,773	33,942	35,167
Commissions and fees	2,644	2,732	7,832	9,096
Commissions and fees—intercompany	0	0	0	0
Principal transactions	2,238	1,327	5,894	5,471
Principal transactions—intercompany	0	0	0	0
Other income	1,399	2,860	5,195	8,164
Other income—intercompany	0	0	0	0
Total non-interest revenues	6,281	6,919	18,921	22,731
Total revenues, net of interest expense	17,760	18,692	52,863	57,898
Provisions for credit losses and for benefits and claims	1,736	1,836	5,190	5,399
Operating expenses
Compensation and benefits	5,203	5,321	15,988	16,324
Compensation and benefits—intercompany	0	0	0	0
Other operating	5,201	5,348	15,308	16,157
Other operating—intercompany	0	0	0	0
Total operating expenses	10,404	10,669	31,296	32,481
Income from continuing operations before income taxes	5,620	6,187	16,377	20,018
Provision for income taxes	1,733	1,881	4,935	6,037
Equity in undistributed income of subsidiaries	0	0	0	0
Income from continuing operations	3,887	4,306	11,442	13,981
Income (loss) from discontinued operations, net of taxes	(30)	(10)	(55)	(9)
Net income before attribution of noncontrolling interests	3,857	4,296	11,387	13,972
Noncontrolling interests	17	5	48	65
Citigroup’s net income	3,840	4,291	11,339	13,907
Comprehensive income
Other comprehensive income (loss)	(1,078)	(2,153)	2,166	(4,041)
Citigroup’s comprehensive income	2,762	2,138	13,505	9,866
Reportable legal entities | Citigroup parent company
Revenues
Dividends from subsidiaries	4,000	3,600	9,700	8,200
Interest revenue	2	2	5	7
Interest revenue—intercompany	695	739	2,235	2,122
Interest expense	1,102	1,121	3,266	3,430
Interest expense—intercompany	61	(80)	140	(411)
Net interest revenue	(466)	(300)	(1,166)	(890)
Commissions and fees	0	0	0	0
Commissions and fees—intercompany	0	0	(19)	0
Principal transactions	(1,103)	735	(1,498)	1,192
Principal transactions—intercompany	977	(774)	1,018	(1,443)
Other income	482	(713)	(3,197)	2,463
Other income—intercompany	(501)	1,012	3,495	(1,602)
Total non-interest revenues	(145)	260	(201)	610
Total revenues, net of interest expense	3,389	3,560	8,333	7,920
Provisions for credit losses and for benefits and claims	0	0	0	0
Operating expenses
Compensation and benefits	26	(70)	18	(22)
Compensation and benefits—intercompany	8	24	34	54
Other operating	(103)	70	377	30
Other operating—intercompany	133	36	213	166
Total operating expenses	64	60	642	228
Income from continuing operations before income taxes	3,325	3,500	7,691	7,692
Provision for income taxes	(395)	(60)	(875)	(786)
Equity in undistributed income of subsidiaries	120	731	2,773	5,429
Income from continuing operations	3,840	4,291	11,339	13,907
Income (loss) from discontinued operations, net of taxes	0	0	0	0
Net income before attribution of noncontrolling interests	3,840	4,291	11,339	13,907
Noncontrolling interests	0	0	0	0
Citigroup’s net income	3,840	4,291	11,339	13,907
Comprehensive income
Other comprehensive income (loss)	(1,078)	(2,153)	2,166	(4,041)
Citigroup’s comprehensive income	2,762	2,138	13,505	9,866
Reportable legal entities | CGMHI
Revenues
Dividends from subsidiaries	0	0	0	0
Interest revenue	1,158	1,116	3,555	3,363
Interest revenue—intercompany	148	60	423	180
Interest expense	345	236	1,110	741
Interest expense—intercompany	401	334	1,246	935
Net interest revenue	560	606	1,622	1,867
Commissions and fees	1,062	1,043	3,141	3,707
Commissions and fees—intercompany	63	29	33	132
Principal transactions	1,600	4,707	3,857	6,896
Principal transactions—intercompany	(470)	(4,418)	(1,513)	(5,252)
Other income	51	299	178	326
Other income—intercompany	51	464	250	1,004
Total non-interest revenues	2,357	2,124	5,946	6,813
Total revenues, net of interest expense	2,917	2,730	7,568	8,680
Provisions for credit losses and for benefits and claims	0	0	0	0
Operating expenses
Compensation and benefits	1,150	1,253	3,641	3,764
Compensation and benefits—intercompany	0	0	0	0
Other operating	444	514	1,242	1,462
Other operating—intercompany	379	298	1,008	903
Total operating expenses	1,973	2,065	5,891	6,129
Income from continuing operations before income taxes	944	665	1,677	2,551
Provision for income taxes	345	293	539	562
Equity in undistributed income of subsidiaries	0	0	0	0
Income from continuing operations	599	372	1,138	1,989
Income (loss) from discontinued operations, net of taxes	0	0	0	0
Net income before attribution of noncontrolling interests	599	372	1,138	1,989
Noncontrolling interests	(9)	9	(10)	6
Citigroup’s net income	608	363	1,148	1,983
Comprehensive income
Other comprehensive income (loss)	(86)	12	(28)	(74)
Citigroup’s comprehensive income	522	375	1,120	1,909
Reportable legal entities | Other Citigroup subsidiaries and eliminations
Revenues
Dividends from subsidiaries	0	0	0	0
Interest revenue	13,493	13,596	39,616	40,817
Interest revenue—intercompany	(843)	(799)	(2,658)	(2,302)
Interest expense	1,727	1,584	4,858	4,849
Interest expense—intercompany	(462)	(254)	(1,386)	(524)
Net interest revenue	11,385	11,467	33,486	34,190
Commissions and fees	1,582	1,689	4,691	5,389
Commissions and fees—intercompany	(63)	(29)	(14)	(132)
Principal transactions	1,741	(4,115)	3,535	(2,617)
Principal transactions—intercompany	(507)	5,192	495	6,695
Other income	866	3,274	8,214	5,375
Other income—intercompany	450	(1,476)	(3,745)	598
Total non-interest revenues	4,069	4,535	13,176	15,308
Total revenues, net of interest expense	15,454	16,002	46,662	49,498
Provisions for credit losses and for benefits and claims	1,736	1,836	5,190	5,399
Operating expenses
Compensation and benefits	4,027	4,138	12,329	12,582
Compensation and benefits—intercompany	(8)	(24)	(34)	(54)
Other operating	4,860	4,764	13,689	14,665
Other operating—intercompany	(512)	(334)	(1,221)	(1,069)
Total operating expenses	8,367	8,544	24,763	26,124
Income from continuing operations before income taxes	5,351	5,622	16,709	17,975
Provision for income taxes	1,783	1,648	5,271	6,261
Equity in undistributed income of subsidiaries	0	0	0	0
Income from continuing operations	3,568	3,974	11,438	11,714
Income (loss) from discontinued operations, net of taxes	(30)	(10)	(55)	(9)
Net income before attribution of noncontrolling interests	3,538	3,964	11,383	11,705
Noncontrolling interests	26	(4)	58	59
Citigroup’s net income	3,512	3,968	11,325	11,646
Comprehensive income
Other comprehensive income (loss)	(1,019)	5,323	2,589	(2,285)
Citigroup’s comprehensive income	2,493	9,291	13,914	9,361
Consolidating adjustments
Revenues
Dividends from subsidiaries	(4,000)	(3,600)	(9,700)	(8,200)
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	(4,000)	(3,600)	(9,700)	(8,200)
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
Income from continuing operations before income taxes	(4,000)	(3,600)	(9,700)	(8,200)
Provision for income taxes	0	0	0	0
Equity in undistributed income of subsidiaries	(120)	(731)	(2,773)	(5,429)
Income from continuing operations	(4,120)	(4,331)	(12,473)	(13,629)
Income (loss) from discontinued operations, net of taxes	0	0	0	0
Net income before attribution of noncontrolling interests	(4,120)	(4,331)	(12,473)	(13,629)
Noncontrolling interests	0	0	0	0
Citigroup’s net income	(4,120)	(4,331)	(12,473)	(13,629)
Comprehensive income
Other comprehensive income (loss)	1,105	(5,335)	(2,561)	2,359
Citigroup’s comprehensive income	$ (3,015)	$ (9,666)	$ (15,034)	$ (11,270)