Significant Accounting Policies - Consolidated Statement of Comprehensive Income as Adjusted (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net income including noncontrolling interest	$ 1,525	$ 1,303	$ 3,152	$ 2,613
Other comprehensive income (loss), net of tax:
Defined benefit pension and postretirement plans adjustment	121	47	240	155
Total other comprehensive income (loss), net of tax	280	117	235	(172)
Comprehensive income (loss) including noncontrolling interest	1,805	1,420	3,387	2,441
Comprehensive income (loss) attributable to 3M	$ 1,805	1,423	$ 3,383	2,445
Under Prior Method
Net income including noncontrolling interest		1,287		2,581
Other comprehensive income (loss), net of tax:
Defined benefit pension and postretirement plans adjustment		58		177
Total other comprehensive income (loss), net of tax		128		(150)
Comprehensive income (loss) including noncontrolling interest		1,415		2,431
Comprehensive income (loss) attributable to 3M		$ 1,418		$ 2,435