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, 2018			$ 16,796	$ 55,151			$ 159,206	$ (168,071)	$ (29,490)	$ 134			$ 16,929
Net income plus other comprehensive income/(loss):
Net income			5,761				5,761						5,761
Other comprehensive income/(loss)			404						404				404
Total comprehensive income/(loss)			6,165										6,165
Cash dividends paid - common stock			(4,269)				(4,269)						(4,269)
Common stock issued under employee plans			657	657									657
Purchases and sales of treasury stock under employee plans - net			(56)				16	(72)					(56)
Other treasury shares purchased, not retired			(1,331)					(1,331)					(1,331)
Changes in other equity			(5)				(5)						(5)
Changes in noncontrolling interests										6			6
Balance at the End of the Period at Sep. 30, 2019			17,956	55,808			160,709	(169,474)	(29,086)	139			18,096
Balance at the Beginning of the Period at Jun. 30, 2019			17,645	55,404			160,467	(169,385)	(28,841)	131			17,776
Net income plus other comprehensive income/(loss):
Net income			1,672				1,672						1,672
Other comprehensive income/(loss)			(245)						(245)				(245)
Total comprehensive income/(loss)			1,427										1,427
Cash dividends paid - common stock			(1,436)				(1,436)						(1,436)
Common stock issued under employee plans			404	404									404
Purchases and sales of treasury stock under employee plans - net			32				6	27					32
Other treasury shares purchased, not retired			(115)					(115)					(115)
Changes in noncontrolling interests										8			8
Balance at the End of the Period at Sep. 30, 2019			17,956	55,808			160,709	(169,474)	(29,086)	139			18,096
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

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