Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	3.2	9.0
Numerator:
Net income attributable to 3M	$ 1,323	$ 1,275
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	598.1	607.4
Dilution associated with the Company's stock-based compensation plans (in shares)	13.9	13.9
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	612.0	621.3
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 2.21	$ 2.10
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 2.16	$ 2.05