Supplemental Equity and Comprehensive Income Information - Dividends (Details) - USD ($) $ / shares in Units, $ in Billions	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Supplemental Equity and Comprehensive Income Information
Cash dividends paid per 3M common share (in dollars per share)	$ 1.025	$ 0.855	$ 1.025	$ 0.855	$ 3.075	$ 2.565
Increase of Current Liabilities due to dividend declared but not paid							$ 0.6	$ 0.6