Supplemental Equity and Comprehensive Income Information - Reclass AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Amount Reclassified from Accumulated Other Comprehensive Income
Net of tax	$ (142)	$ (71)
Gains (losses) associated with defined benefit pension and postretirement plans amortization
Amount Reclassified from Accumulated Other Comprehensive Income
Prior service benefit	19	22
Net actuarial loss	(170)	(141)
Total before tax	(151)	(119)
Tax effect	35	36
Net of tax	(116)	(83)
Cash flow hedging instruments gains (losses)
Amount Reclassified from Accumulated Other Comprehensive Income
Total before tax	(34)	18
Tax effect	8	(6)
Net of tax	(26)	12
Cash flow hedging instruments gains (losses) | Foreign currency forward/option contracts
Amount Reclassified from Accumulated Other Comprehensive Income
Cost of sales	$ (34)	$ 18