Significant Accounting Policies (Details) $ / shares in Units, shares in Millions, VEF in Millions, $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) $ / shares shares	Jun. 30, 2014 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) $ / shares shares	Jun. 30, 2014 USD ($) $ / shares shares	Dec. 31, 2014	Jun. 30, 2015 VEF
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 100
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 - CENCOEX	6		6			6
Exchange rate established by Venezuelan government from bolivars to dollars - SICAD	13		13			13
Exchange rate established by Venezuelan government from bolivars to dollars - SIMADI	200		200			200
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	5.5	3.1	4.5	2.7
Numerator:
Net income attributable to 3M | $	$ 1,300	$ 1,267	$ 2,499	$ 2,474
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	631.3	652.0	633.8	656.7
Dilution associated with the Company's stock-based compensation plans (in shares)	11.7	12.6	12.3	12.9
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	643.0	664.6	646.1	669.6
Earnings per share attributable to 3M common shareholders - basic (in dollars per share) | $ / shares	$ 2.06	$ 1.94	$ 3.94	$ 3.77
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share) | $ / shares	$ 2.02	$ 1.91	$ 3.87	$ 3.70