Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	5.2	1.9
Numerator:
Net income attributable to 3M	$ 891	$ 602
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	577.5	596.2
Dilution associated with the Company's stock-based compensation plans (in shares)	11.0	16.5
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	588.5	612.7
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 1.54	$ 1.01
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 1.51	$ 0.98