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			4,089				4,089						4,089
Other comprehensive income/(loss)			649						649				649
Total comprehensive income/(loss)			4,738										4,738
Cash dividends paid - common stock			(2,833)				(2,833)						(2,833)
Common stock issued under employee plans			254	254									254
Purchases and sales of treasury stock under employee plans - net			(88)				11	(99)					(88)
Other treasury shares purchased, not retired			(1,216)					(1,216)					(1,216)
Changes in other equity			(5)				(5)						(5)
Changes in noncontrolling interests										(3)			(3)
Balance at the End of the Period at Jun. 30, 2019			17,645	55,404			160,467	(169,385)	(28,841)	131			17,776
Balance at the Beginning of the Period at Mar. 31, 2019			16,481	55,287			159,396	(169,021)	(29,182)	126			16,607
Net income plus other comprehensive income/(loss):
Net income			2,498				2,498						2,498
Other comprehensive income/(loss)			340						340				340
Total comprehensive income/(loss)			2,839										2,839
Cash dividends paid - common stock			(1,435)				(1,435)						(1,435)
Common stock issued under employee plans			117	117									117
Purchases and sales of treasury stock under employee plans - net			(40)				9	(49)					(40)
Other treasury shares purchased, not retired			(316)					(316)					(316)
Changes in noncontrolling interests										5			5
Balance at the End of the Period at Jun. 30, 2019			17,645	55,404			160,467	(169,385)	(28,841)	131			17,776
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

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