Supplemental Equity and Comprehensive Income Information - AOCI Reclass (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Amount Reclassified from Accumulated Other Comprehensive Income
Net of tax	$ (55)	$ (65)	$ (190)	$ (185)
Selling, general and administrative expenses	(1,530)	(1,597)	(4,644)	(4,875)
Income before income taxes	1,845	1,880	5,360	5,388
Tax effect	(547)	(569)	(1,558)	(1,569)
Net income attributable to 3M	1,296	1,303	3,795	3,777
Defined Benefit Pension and Postretirement Plans Adjustment
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	(134)	(89)	(399)	(272)
Tax effect	44	30	135	92
Net of tax	(90)	(59)	(264)	(180)
Transition asset
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax		1	1	1
Prior service benefit
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	19	15	54	45
Net actuarial loss
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	(153)	(105)	(471)	(318)
Curtailments/Settlements
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax			17
Cash flow hedging instruments gains (losses)
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	55	(9)	116	(8)
Cash flow hedging instruments gains (losses) | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	55	(9)	116	(8)
Tax effect	(20)	3	(42)	3
Net income attributable to 3M	35	(6)	74	(5)
Cash flow hedging instruments gains (losses) | Foreign currency forward/option contracts | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Cost of sales	$ 55	(7)	120	(9)
Cash flow hedging instruments gains (losses) | Commodity price swap contracts | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Cost of sales		(1)	(2)	2
Cash flow hedging instruments gains (losses) | Interest rate swap contracts | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Interest expense		$ (1)	$ (2)	$ (1)