CONSOLIDATED STATEMENT OF INCOME - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Interest revenue	[1]	$ 61,204	$ 57,615	$ 58,551
Interest expense	[1]	16,517	12,511	11,921
Net interest revenue	[1]	44,687	45,104	46,630
Commissions and fees	[1]	12,939	11,938	14,485
Principal transactions	[1]	9,168	7,585	6,008
Administration and other fiduciary fees	[1]	3,079	2,783	2,856
Realized gains on sales of investments, net	[1]	778	948	682
Other-than-temporary impairment losses on investments
Gross impairment losses	[1]	(63)	(620)	(265)
Less: Impairments recognized in AOCI	[1]	0	0	0
Net impairment losses recognized in earnings	[1]	(63)	(620)	(265)
Other revenue	[1]	861	2,137	5,958
Total non-interest revenues	[1]	26,762	24,771	29,724
Total revenues, net of interest expense	[1]	71,449	69,875	76,354
Provisions for credit losses and for benefits and claims
Provision for loan losses		7,503	6,749	7,108
Policyholder benefits and claims		109	204	731
Provision (release) for unfunded lending commitments		(161)	29	74
Total provisions for credit losses and for benefits and claims		7,451	6,982	7,913
Operating expenses
Compensation and benefits	[1]	21,181	20,970	21,769
Premises and equipment	[1]	2,453	2,542	2,878
Technology/communication	[1]	6,891	6,685	6,581
Advertising and marketing	[1]	1,608	1,632	1,547
Other operating	[1]	9,104	9,587	10,840
Total operating expenses	[1]	41,237	41,416	43,615
Income (loss) from continuing operations before income taxes		22,761	21,477	24,826
Provision for income taxes (benefits)		29,388	6,444	7,440
Income (loss) from continuing operations		(6,627)	15,033	17,386
Discontinued operations
Loss from discontinued operations		(104)	(80)	(83)
Provision (benefit) for income taxes		7	(22)	(29)
Loss from discontinued operations, net of taxes		(111)	(58)	(54)
Net income (loss) before attribution of noncontrolling interests		(6,738)	14,975	17,332
Noncontrolling interests		60	63	90
Citigroup’s net income (loss)		$ (6,798)	$ 14,912	$ 17,242
Basic earnings per share
Income (loss) from continuing operations (in dollars per share)	[2]	$ (2.94)	$ 4.74	$ 5.43
Loss from discontinued operations, net of taxes (in dollars per share)	[2]	(0.04)	(0.02)	(0.02)
Net income (loss) (in dollars per share)	[2]	$ (2.98)	$ 4.72	$ 5.41
Weighted average common shares outstanding (in shares)		2,698.5	2,888.1	3,004.0
Diluted earnings per share
Income (loss) from continuing operations (in dollars per share)	[2]	$ (2.94)	$ 4.74	$ 5.42
Income (loss) from discontinued operations, net of taxes (in dollars per share)	[2]	(0.04)	(0.02)	(0.02)
Net income (loss) (in dollars per share)	[2]	$ (2.98)	$ 4.72	$ 5.40
Adjusted weighted average common shares outstanding (in shares)		2,698.5	2,888.3	3,007.7

[1] Certain prior-period revenue and expense lines and totals were reclassified to conform to the current period’s presentation. See Note 3 to the Consolidated Financial Statements.

[2] Due to rounding, earnings per share on continuing operations and discontinued operations may not sum to earnings per share on net income.