Document and Entity Information - USD ($) shares in Millions, $ in Billions	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Document Information
Entity Registrant Name	3M CO
Entity Central Index Key	0000066740
Document Type	10-K
Document Transition Report	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity File Number	1-3285
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	41-0417775
Entity Address, Address Line One	3M Center
Entity Address, City or Town	St. Paul
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55144
City Area Code	651
Local Phone Number	733-1110
Entity Well Known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float		$ 91.3	$ 99.7
Entity Common Stock, Shares Outstanding		575.6
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Common Stock | New York Stock Exchange, Inc.
Document Information
Title of 12(b) Security	Common Stock, Par Value $.01 Per Share
Trading Symbol	MMM
Security Exchange Name	NYSE
Common Stock | Chicago Stock Exchange, Inc.
Document Information
Title of 12(b) Security	Common Stock, Par Value $.01 Per Share
Trading Symbol	MMM
Security Exchange Name	CHX
1.500% Notes due 2026 | New York Stock Exchange, Inc.
Document Information
Title of 12(b) Security	1.500% Notes due 2026
Trading Symbol	MMM26
Security Exchange Name	NYSE
Floating Rate Notes due 2020 | New York Stock Exchange, Inc.
Document Information
Title of 12(b) Security	Floating Rate Notes due 2020
No Trading Symbol Flag	true
0.375% Notes due 2022 | New York Stock Exchange, Inc.
Document Information
Title of 12(b) Security	0.375% Notes due 2022
Trading Symbol	MMM22A
Security Exchange Name	NYSE
0.950% Notes due 2023 | New York Stock Exchange, Inc.
Document Information
Title of 12(b) Security	0.950% Notes due 2023
Trading Symbol	MMM23
Security Exchange Name	NYSE
1.750% Notes due 2030 | New York Stock Exchange, Inc.
Document Information
Title of 12(b) Security	1.750% Notes due 2030
Trading Symbol	MMM30
Security Exchange Name	NYSE
1.500% Notes due 2031 | New York Stock Exchange, Inc.
Document Information
Title of 12(b) Security	1.500% Notes due 2031
Trading Symbol	MMM31
Security Exchange Name	NYSE