CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Citigroup’s net income (loss)		$ (6,798)	$ 14,912	$ 17,242
Add: Citigroup’s other comprehensive income (loss)
Net change in unrealized gains and losses on investment securities, net of taxes		(863)	108	(964)
Net change in debt valuation adjustment (DVA), net of taxes	[1]	(569)	(337)	0
Net change in cash flow hedges, net of taxes		(138)	57	292
Benefit plans liability adjustment, net of taxes	[2]	(1,019)	(48)	43
Net change in foreign currency translation adjustment, net of taxes and hedges		(202)	(2,802)	(5,499)
Citigroup’s total other comprehensive income (loss)	[3]	(2,791)	(3,022)	(6,128)
Citigroup’s total comprehensive income (loss)		(9,589)	11,890	11,114
Add: Other comprehensive income (loss) attributable to noncontrolling interests		114	(56)	(83)
Add: Net income attributable to noncontrolling interests		60	63	90
Total comprehensive income (loss)		$ (9,415)	$ 11,897	$ 11,121

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

[2] See Note 8 to the Consolidated Financial Statements.

[3] Includes the impact of ASU 2018-02, adopted in the fourth quarter of 2017. See Note 1 to the Consolidated Financial Statements.