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			4,234				4,234						4,234
Other comprehensive income/(loss)			12						12				12
Total comprehensive income/(loss)			4,247										4,247
Cash dividends paid - common stock			(4,343)				(4,343)						(4,343)
Common stock issued under employee plans			471	471									471
Purchases and sales of treasury stock under employee plans - net			59				26	33					59
Changes in noncontrolling interests										(18)			(18)
Balance at the End of the Period at Sep. 30, 2020			21,208	56,366			162,806	(169,380)	(28,584)	126			21,334
Balance at the Beginning of the Period at Jun. 30, 2020			20,551	56,135			162,559	(169,386)	(28,757)	137			20,688
Net income plus other comprehensive income/(loss):
Net income			1,698				1,698						1,698
Other comprehensive income/(loss)			172						172				172
Total comprehensive income/(loss)			1,870										1,870
Cash dividends paid - common stock			(1,453)				(1,453)						(1,453)
Common stock issued under employee plans			232	232									232
Purchases and sales of treasury stock under employee plans - net			9				2	7					9
Changes in noncontrolling interests										(11)			(11)
Balance at the End of the Period at Sep. 30, 2020			21,208	56,366			162,806	(169,380)	(28,584)	126			21,334
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			3,410				3,410						3,410
Other comprehensive income/(loss)			2,035						2,035				2,035
Total comprehensive income/(loss)			5,446										5,446
Cash dividends paid - common stock			(4,395)				(4,395)						(4,395)
Common stock issued under employee plans			632	632									632
Purchases and sales of treasury stock under employee plans - net			(52)				15	(66)					(52)
Changes in noncontrolling interests										(1)			(1)
Balance at the End of the Period at Sep. 30, 2021			22,228	57,189			161,747	(169,406)	(27,302)	129			22,357
Balance at the Beginning of the Period at Jun. 30, 2021			21,942	56,912			162,086	(169,404)	(27,652)	125			22,067
Net income plus other comprehensive income/(loss):
Net income			1,130				1,130						1,130
Other comprehensive income/(loss)			350						350				350
Total comprehensive income/(loss)			1,480										1,480
Cash dividends paid - common stock			(1,471)				(1,471)						(1,471)
Common stock issued under employee plans			277	277									277
Purchases and sales of treasury stock under employee plans - net			0				1	(2)					0
Changes in noncontrolling interests										4			4
Balance at the End of the Period at Sep. 30, 2021			$ 22,228	$ 57,189			$ 161,747	$ (169,406)	$ (27,302)	$ 129			$ 22,357

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