Significant Accounting Policies - Consolidated Statement of Income as Adjusted (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other expense (income), net	$ 31	$ 83	$ 113	$ 248
Income before income taxes	1,757	1,826	5,640	5,064
Provision for income taxes	324	391	1,058	1,016
Income of consolidated group	1,433	1,435	4,582	4,048
Net income including noncontrolling interest	1,437	1,434	4,589	4,047
Net income attributable to 3M	$ 1,434	$ 1,430	$ 4,582	$ 4,044
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 2.47	$ 2.47	$ 7.90	$ 7.01
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 2.45	$ 2.45	$ 7.81	$ 6.95
Under Prior Method
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other expense (income), net		$ 104		$ 311
Income before income taxes		1,805		5,001
Provision for income taxes		387		1,002
Income of consolidated group		1,418		3,999
Net income including noncontrolling interest		1,417		3,998
Net income attributable to 3M		$ 1,413		$ 3,995
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)		$ 2.45		$ 6.92
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)		$ 2.43		$ 6.87