Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	8.7	19.2
Numerator:
Net income attributable to 3M	$ 1,624	$ 1,308
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	580.5	576.8
Dilution associated with the Company's stock-based compensation plans (in shares)	5.8	4.7
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	586.3	581.5
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 2.80	$ 2.27
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 2.77	$ 2.25