Significant Accounting Policies - Consolidated Statement of Income as Adjusted (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other expense (income), net	$ 33	$ 90	$ 82	$ 165
Income before income taxes	1,938	1,650	3,883	3,238
Provision for income taxes	415	347	734	625
Income of consolidated group	1,523	1,303	3,149	2,613
Net income including noncontrolling interest	1,525	1,303	3,152	2,613
Net income attributable to 3M	$ 1,524	$ 1,306	$ 3,148	$ 2,614
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 2.62	$ 2.26	$ 5.42	$ 4.53
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 2.59	$ 2.25	$ 5.36	$ 4.50
Under Prior Method
Other expense (income), net		$ 111		$ 207
Income before income taxes		1,629		3,196
Provision for income taxes		342		615
Income of consolidated group		1,287		2,581
Net income including noncontrolling interest		1,287		2,581
Net income attributable to 3M		$ 1,290		$ 2,582
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)		$ 2.24		$ 4.48
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)		$ 2.22		$ 4.44