Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	19.2	5.2
Numerator:
Net income attributable to 3M	$ 1,292	$ 891
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	576.8	577.5
Dilution associated with the Company's stock-based compensation plans (in shares)	4.7	11.0
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	581.5	588.5
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 2.24	$ 1.54
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 2.22	$ 1.51