Quarterly Data (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Data (Unaudited)
Net sales	$ 7,719	$ 8,137	$ 8,134	$ 7,831	$ 7,569	$ 7,916	$ 7,752	$ 7,634	$ 31,821	$ 30,871	$ 29,904
Cost of sales	4,027	4,205	4,184	4,031	3,976	4,148	4,013	3,969	16,447	16,106	15,685
Net income including noncontrolling interest	1,179	1,311	1,283	1,225	1,116	1,245	1,213	1,147	4,998	4,721	4,511
Net income attributable to 3M	$ 1,179	$ 1,303	$ 1,267	$ 1,207	$ 1,103	$ 1,230	$ 1,197	$ 1,129	$ 4,956	$ 4,659	$ 4,444
Earnings per share attributable to 3M common shareholders - basic (in dollars per share)	$ 1.85	$ 2.02	$ 1.94	$ 1.83	$ 1.65	$ 1.81	$ 1.74	$ 1.63	$ 7.63	$ 6.83	$ 6.40
Earnings per share attributable to 3M common shareholders - diluted (in dollars per share)	$ 1.81	$ 1.98	$ 1.91	$ 1.79	$ 1.62	$ 1.78	$ 1.71	$ 1.61	$ 7.49	$ 6.72	$ 6.32