SUPPLEMENTARY INFORMATION (Sundry Income, Net) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplementary Information [Line Items]
Non-operating pension and other postretirement benefit plan net credit	$ 119	$ (682)	$ 34
Gain on sales of other assets and investments	59	182	170
Interest income	109	106	107
Foreign exchange losses	(119)	(72)	(126)
Gain (loss) on divestiture	(14)	0	(25)
Gain and post-close adjustments related to Dow Silicones ownership restructure	(47)	0	2,445
Deferred Tax Assets, Loss and Credit Carryforwards	2,244	1,734
Loss on early extinguishment of debt	(54)	0	0
Costs associated with transactions and productivity actions	0	0	(41)
Reclassification of cumulative translation adjustments	4	8	0
Other - net	104	116	125
Sundry income (expense) - net	181	195	1,486
Dow Silicones Corporation
Supplementary Information [Line Items]
Gain and post-close adjustments related to Dow Silicones ownership restructure	(47)	0	2,445
Breast Implant and Other Products Liability Claims \| Impact to Sundry income (expense)
Supplementary Information [Line Items]
Implant liability adjustment	0	0	27
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| MEGlobal
Supplementary Information [Line Items]
Gain (loss) on divestiture	20	0	(1)
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Dow AgroSciences' Corn Seed Business
Supplementary Information [Line Items]
Gain (loss) on divestiture	0	635	0
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Global Ethylene Acrylic Acid (EAA)
Supplementary Information [Line Items]
Gain (loss) on divestiture	0	227	0
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations \| Chlorine Value Chain
Supplementary Information [Line Items]
Gain (loss) on divestiture	0	7	6
Nova Patent Infringement
Supplementary Information [Line Items]
Gain (loss) related to litigation settlement	0	137	0
Bayer CropScience v. Dow AgroSciences
Supplementary Information [Line Items]
Gain (loss) related to litigation settlement	0	(469)	0
Urethane Matters Class Action Lawsuit And Opt-Out Cases
Supplementary Information [Line Items]
Gain (loss) related to litigation settlement	$ 0	$ 0	$ (1,235)

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