Supplemental Equity and Comprehensive Income Information (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Amount Reclassified from Accumulated Other Comprehensive Income
Selling, general and administrative expenses	$ (1,564)	$ (1,632)
Total before tax	213	101
Tax effect	(502)	(463)
Net of tax	1,167	1,279
Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Net of tax	(61)	(57)
Gains (losses) associated with defined benefit pension and postretirement plans amortization
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	148	91
Gains (losses) associated with defined benefit pension and postretirement plans amortization | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Transition asset	0	0
Prior service benefit	18	15
Net actuarial loss	(159)	(106)
Curtailments/Settlements	17	0
Total before tax	(124)	(91)
Tax effect	46	30
Net of tax	(78)	(61)
Debt and equity security gains (losses)
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	0	2
Debt and equity security gains (losses) | Reclassifications out of Accumulated Other Comprehensive Income Attributable to 3M
Amount Reclassified from Accumulated Other Comprehensive Income
Selling, general and administrative expenses	0	0
Total before tax	0	0
Tax effect	0	0
Net of tax	0	0
Cash flow hedging instruments gains (losses)
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	109	3
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	27	6
Tax effect	(10)	(2)
Net of tax	17	4
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	30	4
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	(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)	$ 0