Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	1.9	3.2
Numerator:
Net income attributable to 3M	$ 602	$ 1,323
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	596.2	598.1
Dilution associated with the Company's stock-based compensation plans (in shares)	16.5	13.9
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	612.7	612.0
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 1.01	$ 2.21
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 0.98	$ 2.16