Significant Accounting Policies - Consolidated Statement of Income as Adjusted (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Other expense (income), net	$ 49	$ 75
Income before income taxes	1,945	1,588
Provision for income taxes	319	278
Income of consolidated group	1,626	1,310
Net income including noncontrolling interest	1,627	1,310
Net income attributable to 3M	$ 1,624	$ 1,308
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 2.80	$ 2.27
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 2.77	$ 2.25
Under Prior Method
Other expense (income), net		$ 96
Income before income taxes		1,567
Provision for income taxes		273
Income of consolidated group		1,294
Net income including noncontrolling interest		1,294
Net income attributable to 3M		$ 1,292
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)		$ 2.24
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)		$ 2.22