Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings per share
Options outstanding not included in computation of diluted earnings per share (in shares)	3.5		2.7	1.6
Numerator:
Net income attributable to 3M	$ 1,857	$ 1,583	$ 2,459	$ 2,906
Denominator:
Denominator for weighted average 3M common shares outstanding - basic (in shares)	591.4	598.1	593.8	598.1
Dilution associated with the Company's stock-based compensation plans (in shares)	12.8	14.7	14.7	14.3
Denominator for weighted average 3M common shares outstanding - diluted (in shares)	604.2	612.8	608.5	612.4
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 3.14	$ 2.65	$ 4.14	$ 4.86
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 3.07	$ 2.58	$ 4.04	$ 4.74