Significant Accounting Policies (Details) $ / shares in Units, shares in Millions, VEF in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($) $ / shares shares	Dec. 31, 2014	Sep. 30, 2015 VEF	Sep. 30, 2015 USD ($)
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 assets in Venezuelan bolivars | VEF						VEF 500
Maximum balance of intercompany receivables due to 3M Company from its Venezuelan subsidiary | $							$ 25
Exchange rate established by Venezuelan government from bolivars to dollars - CENCOEX						6	6
Exchange rate established by Venezuelan government from bolivars to dollars - SICAD						13	13
Exchange rate established by Venezuelan government from bolivars to dollars - SIMADI						200	200
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	5.5		4.8	1.8
Numerator:
Net income attributable to 3M | $	$ 1,296	$ 1,303	$ 3,795	$ 3,777
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	620.6	645.3	629.4	652.9
Dilution associated with the Company's stock-based compensation plans (in shares)	10.6	12.6	11.8	12.8
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	631.2	657.9	641.2	665.7
Earnings per share attributable to 3M common shareholders - basic (in dollars per share) | $ / shares	$ 2.09	$ 2.02	$ 6.03	$ 5.78
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share) | $ / shares	$ 2.05	$ 1.98	$ 5.92	$ 5.67