CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Millions	Total IBM Stockholders' Equity	Common Stock and Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income/(Loss)	Non-Controlling Interests	Total
Balance at the Beginning of the Period at Dec. 31, 2017	$ 17,594	$ 54,566	$ 153,126	$ (163,507)	$ (26,592)	$ 131	$ 17,725
Equity
Cumulative effect of change in accounting principle | Accounting Standards Update 2014-09, Revenue from Contracts with Customers	524		524				524
Cumulative effect of change in accounting principle | Accounting Standards Updates 2016-01 (Financial Instruments), 2017-12 (Hedging) and 2018-02 (Stranded Tax Effects)			2,422		(2,422)
Net income plus other comprehensive income/(loss)
Net income	1,679		1,679				1,679
Other comprehensive income/(loss)	430				430		430
Total comprehensive income/(loss)	2,109						2,109
Cash dividends paid - common stock ($1.57 and $1.50 per share for 2019 and 2018, respectively)	(1,382)		(1,382)				(1,382)
Common stock issued under employee plans (Shares - 1,391,989 and 1,037,255 for 2019 and 2018, respectively)	146	146					146
Purchases (Shares - 454,710 and 325,635) and sales (Shares - 82,862 and 45,878 ) of treasury stock under employee plans - net, for 2019 and 2018, respectively	(45)		1	(47)			(45)
Other treasury shares purchased, not retired (Shares - 6,856,678 and 4,968,417 for 2019 and 2018, respectively)	(780)			(780)			(780)
Changes in noncontrolling interests						(7)	(7)
Balance at the End of the Period at Mar. 31, 2018	18,166	54,712	156,371	(164,334)	(28,583)	124	18,290
Balance at the Beginning of the Period at Dec. 31, 2017	17,594	54,566	153,126	(163,507)	(26,592)	131	17,725
Balance at the End 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	1,591		1,591				1,591
Other comprehensive income/(loss)	308				308		308
Total comprehensive income/(loss)	1,899						1,899
Cash dividends paid - common stock ($1.57 and $1.50 per share for 2019 and 2018, respectively)	(1,397)		(1,397)				(1,397)
Common stock issued under employee plans (Shares - 1,391,989 and 1,037,255 for 2019 and 2018, respectively)	137	137					137
Purchases (Shares - 454,710 and 325,635) and sales (Shares - 82,862 and 45,878 ) of treasury stock under employee plans - net, for 2019 and 2018, respectively	(48)		2	(50)			(48)
Other treasury shares purchased, not retired (Shares - 6,856,678 and 4,968,417 for 2019 and 2018, respectively)	(900)			(900)			(900)
Changes in other equity	(5)		(5)				(5)
Changes in noncontrolling interests						(8)	(8)
Balance at the End of the Period at Mar. 31, 2019	$ 16,481	$ 55,287	$ 159,396	$ (169,021)	$ (29,182)	$ 126	$ 16,607