Significant Accounting Policies (Details) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended				3 Months Ended
	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 VEF	Jun. 30, 2014 Business Segments Electronics and Energy Divisions
Basis Of Presentation
Number of existing divisions affected by division combination													3
Number of affected divisions that exist after the division combination													2
Foreign Currency Translation
Threshold percentage used to determine if economic environment is highly inflationary									100.00%
Number of years used to determine if economic environment is highly inflationary									3 years
Operating income of Venezuelan subsidiary as percent of consolidated amount high end of range									1.00%
Cumulative inflation rate of Venezuela in November 2009 and since, low end of range									100.00%
Maximum balance of company's net monetary liabilities in Venezuelan bolivars												150
Maximum balance of intercompany receivables due to 3M Company from its Venezuelan subsidiary	20								20
Exchange rate established by Venezuelan government from bolivars to dollars - SICAD1	10								10
Exchange rate established by Venezuelan government from bolivars to dollars - SICAD2	50								50
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)									1.4	2.0	12.6
Numerator:
Net income attributable to 3M	$ 1,179	$ 1,303	$ 1,267	$ 1,207	$ 1,103	$ 1,230	$ 1,197	$ 1,129	$ 4,956	$ 4,659	$ 4,444
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)									649.2	681.9	693.9
Dilution associated with the Company's stock-based compensation plans (in shares)									12.8	11.7	9.4
Denominator for weighted average 3M common shares outstanding - diluted (in shares)									662.0	693.6	703.3
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 1.85	$ 2.02	$ 1.94	$ 1.83	$ 1.65	$ 1.81	$ 1.74	$ 1.63	$ 7.63	$ 6.83	$ 6.40
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 1.81	$ 1.98	$ 1.91	$ 1.79	$ 1.62	$ 1.78	$ 1.71	$ 1.61	$ 7.49	$ 6.72	$ 6.32