Supplemental Equity and Comprehensive Income Information - Reclassifications out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Amount Reclassified from Accumulated Other Comprehensive Income
Other expense (income), net	$ (31)	$ (83)	$ (113)	$ (248)
Total before tax	1,757	1,826	5,640	5,064
Tax effect	324	391	1,058	1,016
Net income	1,437	1,434	4,589	4,047
Cost of sales	4,853	4,303	14,097	12,217
Net income attributable to 3M	1,434	1,430	4,582	4,044
Reclassification out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income
Net income attributable to 3M	(133)	(100)	(389)	(286)
Defined benefit pension and postretirement plans adjustments | Reclassification out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	(158)	(149)	(477)	(446)
Tax effect	39	33	118	108
Net income	(119)	(116)	(359)	(338)
Transition asset | Reclassification out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income
Other expense (income), net	(1)	(1)	(2)	(2)
Prior service benefit | Reclassification out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income
Other expense (income), net	15	15	45	46
Net actuarial loss | Reclassification out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income
Other expense (income), net	(172)	(162)	(518)	(487)
Curtailments/Settlements | Reclassification out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income
Other expense (income), net	0	(1)	(2)	(3)
Cash flow hedging instruments gains (losses) | Reclassification out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income
Other expense (income), net	(3)	(2)	(7)	(6)
Total before tax	(18)	21	(39)	68
Tax effect	4	(5)	9	(16)
Net income	(14)	16	(30)	52
Cost of sales	$ (15)	$ 23	$ (32)	$ 74