Document and Entity Information	9 Months Ended
	Sep. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	3M CO
Entity Central Index Key	0000066740
Document Type	10-Q
Document Period End Date	Sep. 30, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	640,818,842
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q3