CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Millions		Total	Citigroup stockholders' equity	Preferred stock at aggregate liquidation value	Citigroup common stockholders' equity	Common stock and additional paid-in capital	Retained earnings		Treasury stock, at cost		Citigroup's accumulated other comprehensive income (loss)		Noncontrolling interests
Increase (Decrease) in Stockholders' Equity
Adjusted balance							$ 133,856				$ (29,359)
Balance, beginning of year at Dec. 31, 2015				$ 16,718		$ 108,319	133,841		$ (7,677)		(29,344)		$ 1,235
Balance, beginning of year (in shares) at Dec. 31, 2015				(669)		(3,099,482)			(146,203)
Adjustment to opening balance, net of taxes at Dec. 31, 2015	[1]						15				(15)
Increase (Decrease) in Stockholders' Equity
Citigroup’s net income (loss)		$ 14,912					14,912
Issuance of new preferred stock				$ 2,535
Issuance of new preferred stock (in shares)				101
Employee benefit plans						$ (251)			$ 826	[2]
Employee benefit plans (in shares)	[2]								14,256
Preferred stock issuance expense						(37)
Other						42							(36)
Net income attributable to noncontrolling-interest shareholders		14,975											63
Common dividends	[3]						(1,214)
Preferred dividends		(1,077)					(1,077)
Transactions between noncontrolling-interest shareholders and the related consolidated subsidiary													(11)
Transactions between Citigroup and the noncontrolling-interest shareholders													(130)
Treasury stock acquired	[4]								$ (9,451)
Treasure stock acquired (in shares)	[4]								(195,143)
Dividends paid to noncontrolling-interest shareholders													(42)
Other comprehensive income (loss)		(3,022)									(3,022)	[5]	(56)
Net change in noncontrolling interests													(212)
Balance, end of year at Dec. 31, 2016		226,143	$ 225,120	$ 19,253	$ 205,867	$ 108,073	146,477		$ (16,302)		(32,381)		1,023
Balance, end of year (in shares) at Dec. 31, 2016				(770)	(2,772,392)	(3,099,482)			(327,090)
Increase (Decrease) in Stockholders' Equity
Adjusted balance							145,817				(31,877)
Adjustment to opening balance, net of taxes at Dec. 31, 2016	[1]						(660)				504
Increase (Decrease) in Stockholders' Equity
Citigroup’s net income (loss)		(6,798)					(6,798)
Employee benefit plans						$ (27)			$ 531	[2]
Employee benefit plans (in shares)						41			11,651	[2]
Other						$ (7)	(90)	[6]					(72)
Net income attributable to noncontrolling-interest shareholders		(6,738)											60
Common dividends	[3]						(2,595)
Preferred dividends		(1,213)					(1,213)
Impact of Tax Reform related to AOCI reclassification							3,304	[5]			(3,304)
Transactions between noncontrolling-interest shareholders and the related consolidated subsidiary													(28)
Transactions between Citigroup and the noncontrolling-interest shareholders													(121)
Treasury stock acquired	[4]								$ (14,538)
Treasure stock acquired (in shares)	[4]								(214,176)
Dividends paid to noncontrolling-interest shareholders													(44)
Other comprehensive income (loss)		(2,791)									(2,791)	[5]	114
Net change in noncontrolling interests													(91)
Balance, end of year at Dec. 31, 2017		201,672	200,740	$ 19,253	$ 181,487	$ 108,039	138,425		$ (30,309)		(34,668)		932
Balance, end of year (in shares) at Dec. 31, 2017				(770)	(2,569,908)	(3,099,523)			(529,615)
Increase (Decrease) in Stockholders' Equity
Adjusted balance							138,341				(34,671)
Adjustment to opening balance, net of taxes at Dec. 31, 2017	[1]						(84)				(3)
Increase (Decrease) in Stockholders' Equity
Citigroup’s net income (loss)		18,045					18,045
Redemption of preferred stock				$ (793)
Redemption of preferred stock (in shares)				(32)
Employee benefit plans						$ (94)			$ 484	[2]
Employee benefit plans (in shares)						44			10,557	[2]
Other						$ 8							18
Net income attributable to noncontrolling-interest shareholders		18,080											35
Common dividends	[3]						(3,865)
Preferred dividends		(1,173)					(1,174)
Transactions between noncontrolling-interest shareholders and the related consolidated subsidiary													0
Transactions between Citigroup and the noncontrolling-interest shareholders													(50)
Treasury stock acquired	[4]								$ (14,545)
Treasure stock acquired (in shares)	[4]								(212,042)
Dividends paid to noncontrolling-interest shareholders													(38)
Other comprehensive income (loss)		(2,499)									(2,499)	[5]	(43)
Net change in noncontrolling interests													(78)
Balance, end of year at Dec. 31, 2018		$ 197,074	$ 196,220	$ 18,460	$ 177,760	$ 107,953	$ 151,347		$ (44,370)		$ (37,170)		$ 854
Balance, end of year (in shares) at Dec. 31, 2018				(738)	(2,368,467)	(3,099,567)			(731,100)

[1] See Note 1 to the Consolidated Financial Statements for additional details.

[2] Includes treasury stock related to (i) certain activity on employee stock option program exercises, where the employee delivers existing shares to cover the option exercise, or (ii) under Citi’s employee-restricted or deferred-stock programs, where shares are withheld to satisfy tax requirements.

[3] Common dividends declared were $0.32 per share in the first and second quarters and $0.45 per share in the third and fourth quarters of 2018; $0.16 per share in the first and second quarters and $0.32 per share in the third and fourth quarters of 2017; and $0.05 in the first and second quarters and $0.16 per share in the third and fourth quarters of 2016.

[4] For 2018, 2017, and 2016, primarily consists of open market purchases under Citi’s Board of Directors-approved common stock repurchase program.

[5] Includes the impact of ASU 2018-02, which transferred those amounts from AOCI to Retained earnings. See Notes 1 and 19 to the Consolidated Financial Statements.

[6] Includes the impact of ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. See Note 1 to the Consolidated Financial Statements.