CONSOLIDATED STATEMENT OF EQUITY - USD ($) $ in Millions	Total IBM Stockholders' Equity Cumulative Effect, Period of Adoption, Adjustment	[1]	Total IBM Stockholders' Equity	Common Stock and Additional Paid-in Capital	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	[1]	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income/(Loss)	Non-Controlling Interests	Cumulative Effect, Period of Adoption, Adjustment	[1]	Total
Balance at the Beginning of the Period at Dec. 31, 2019	$ (66)		$ 20,841	$ 55,895	$ (66)		$ 162,954	$ (169,413)	$ (28,597)	$ 144	$ (66)		$ 20,985
Net income plus other comprehensive income/(loss):
Net income			2,536				2,536						2,536
Other comprehensive income/(loss)			(160)						(160)				(160)
Total comprehensive income/(loss)			2,377										2,377
Cash dividends paid - common stock			(2,890)				(2,890)						(2,890)
Common stock issued under employee plans			239	239									239
Purchases and sales of treasury stock under employee plans - net			50				24	26					50
Changes in noncontrolling interests										(7)			(7)
Balance at the End of the Period at Jun. 30, 2020			20,551	56,135			162,559	(169,386)	(28,757)	137			20,688
Balance at the Beginning of the Period at Mar. 31, 2020			19,999	56,092			162,626	(169,437)	(29,283)	129			20,128
Net income plus other comprehensive income/(loss):
Net income			1,361				1,361						1,361
Other comprehensive income/(loss)			527						527				527
Total comprehensive income/(loss)			1,888										1,888
Cash dividends paid - common stock			(1,450)				(1,450)						(1,450)
Common stock issued under employee plans			42	42									42
Purchases and sales of treasury stock under employee plans - net			72				22	50					72
Changes in noncontrolling interests										8			8
Balance at the End of the Period at Jun. 30, 2020			20,551	56,135			162,559	(169,386)	(28,757)	137			20,688
Balance at the Beginning of the Period at Dec. 31, 2020			20,597	56,556			162,717	(169,339)	(29,337)	129			20,727
Net income plus other comprehensive income/(loss):
Net income			2,280				2,280						2,280
Other comprehensive income/(loss)			1,685						1,685				1,685
Total comprehensive income/(loss)			3,965										3,965
Cash dividends paid - common stock			(2,924)				(2,924)						(2,924)
Common stock issued under employee plans			355	355									355
Purchases and sales of treasury stock under employee plans - net			(51)				13	(65)					(51)
Changes in noncontrolling interests										(4)			(4)
Balance at the End of the Period at Jun. 30, 2021			21,942	56,912			162,086	(169,404)	(27,652)	125			22,067
Balance at the Beginning of the Period at Mar. 31, 2021			21,389	56,788			162,218	(169,360)	(28,257)	124			21,513
Net income plus other comprehensive income/(loss):
Net income			1,325				1,325						1,325
Other comprehensive income/(loss)			605						605				605
Total comprehensive income/(loss)			1,930										1,930
Cash dividends paid - common stock			(1,467)				(1,467)						(1,467)
Common stock issued under employee plans			124	124									124
Purchases and sales of treasury stock under employee plans - net			(33)				11	(44)					(33)
Changes in noncontrolling interests										1			1
Balance at the End of the Period at Jun. 30, 2021			$ 21,942	$ 56,912			$ 162,086	$ (169,404)	$ (27,652)	$ 125			$ 22,067

[1] * Reflects the adoption of the FASB guidance on current expected credit losses. Refer to note 2, “Accounting Changes.”