Supplemental Equity and Comprehensive Income Information (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Amount Reclassified from Accumulated Other Comprehensive Income
Selling, general and administrative expenses	$ (6,469)	$ (6,384)	$ (6,102)
Total before tax	(2,964)	1,492	481
Tax effect	(2,028)	(1,841)	(1,840)
Net of tax	2,555	5,496	4,719
Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Net of tax	(236)	(449)	(350)
Defined Benefit Pension and Postretirement Plans Adjustment
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	(2,278)	1,930	411
Defined Benefit Pension and Postretirement Plans Adjustment | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Transition asset	1	1	1
Prior service benefit	59	77	84
Net actuarial loss	(420)	(647)	(700)
Total before tax	(360)	(569)	(615)
Tax effect	122	197	219
Net of tax	(238)	(372)	(396)
Debt and Equity Securities, Unrealized Gain (Loss)
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	3	0	6
Debt and Equity Securities, Unrealized Gain (Loss) | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Selling, general and administrative expenses	(1)	0	0
Total before tax	(1)	0	0
Tax effect	0	0	0
Net of tax	(1)	0	0
Cash Flow Hedging Instruments Unrealized Gain (Loss)
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	167	24	(69)
Cash Flow Hedging Instruments Unrealized Gain (Loss) | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	4	(122)	72
Tax effect	(1)	45	(26)
Net of tax	3	(77)	46
Cash Flow Hedging Instruments Unrealized Gain (Loss) | 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	3	(11)	41
Cash Flow Hedging Instruments Unrealized Gain (Loss) | Foreign currency forward contracts | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Interest expense	0	(108)	42
Cash Flow Hedging Instruments Unrealized Gain (Loss) | Commodity price swap contracts | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Cost of sales	2	(2)	(10)
Cash Flow Hedging Instruments Unrealized Gain (Loss) | Interest rate swap contracts | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Interest expense	$ (1)	$ (1)	$ (1)