CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ 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
Balance, beginning of period at Dec. 31, 2016				$ 19,253		$ 108,073	$ 146,477		$ (16,302)		$ (32,381)	$ 1,023
Increase (Decrease) in Stockholders' Equity
Redemption of preferred stock				0
Adjustment to opening balance, net of taxes at Dec. 31, 2016	[1]						(660)				504
Adjusted balance, beginning of period at Dec. 31, 2016							145,817				(31,877)
Increase (Decrease) in Stockholders' Equity
Employee benefit plans						(239)			523	[2]
Other						(5)	(90)	[3]				(53)
Citigroup’s net income		$ 8,004					7,962					42
Distributions paid to noncontrolling-interest shareholders												0
Common dividends	[4]						(890)
Preferred dividends		(621)					(621)
Treasury stock acquired	[5]								(3,563)
Citigroup's total other comprehensive income (loss)											1,978	70
Transactions between Citigroup and the noncontrolling-interest shareholders												6
Net change in noncontrolling interests												65
Balance, end of period at Jun. 30, 2017		231,107	$ 230,019	19,253	$ 210,766	107,829	152,178		(19,342)		(29,899)	1,088
Balance, beginning of period at Mar. 31, 2017											(30,413)
Increase (Decrease) in Stockholders' Equity
Citigroup’s net income		3,904
Preferred dividends		(320)
Citigroup's total other comprehensive income (loss)											514
Balance, end of period at Jun. 30, 2017		231,107	230,019	19,253	210,766	107,829	152,178		(19,342)		(29,899)	1,088
Balance, beginning of period at Dec. 31, 2017		201,672		19,253		108,039	138,425		(30,309)		(34,668)	932
Increase (Decrease) in Stockholders' Equity
Redemption of preferred stock				(218)
Adjustment to opening balance, net of taxes at Dec. 31, 2017	[1]						(84)				(3)
Adjusted balance, beginning of period at Dec. 31, 2017							138,341				(34,671)
Increase (Decrease) in Stockholders' Equity
Employee benefit plans						(285)			471	[2]
Other						1	0	[3]				(11)
Citigroup’s net income		9,158					9,110					48
Distributions paid to noncontrolling-interest shareholders												(36)
Common dividends	[4]						(1,650)
Preferred dividends		(590)					(590)
Treasury stock acquired	[5]								(4,575)
Citigroup's total other comprehensive income (loss)											(2,823)	(43)
Transactions between Citigroup and the noncontrolling-interest shareholders												(16)
Net change in noncontrolling interests												(58)
Balance, end of period at Jun. 30, 2018		200,968	200,094	19,035	181,059	107,755	145,211		(34,413)		(37,494)	874
Balance, beginning of period at Mar. 31, 2018											(34,619)
Increase (Decrease) in Stockholders' Equity
Citigroup’s net income		4,516
Preferred dividends		(318)
Citigroup's total other comprehensive income (loss)											(2,875)
Balance, end of period at Jun. 30, 2018		$ 200,968	$ 200,094	$ 19,035	$ 181,059	$ 107,755	$ 145,211		$ (34,413)		$ (37,494)	$ 874

[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] Includes the impact of ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. See Note 1 to the Consolidated Financial Statements.

[4] Common dividends declared were $0.32 per share in the first and second quarters of 2018 and $0.16 per share in the first and second quarters of 2017.

[5] For the six months ended June 30, 2018 and 2017, primarily consists of open market purchases under Citi’s Board of Directors-approved common stock repurchase program.