Segment Reporting Sig Items (Details) - USD ($) $ in Millions		3 Months Ended																4 Months Ended	8 Months Ended	12 Months Ended
		Dec. 31, 2019	[1]	Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018	[1]	Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017	Aug. 31, 2017	Dec. 31, 2019		Dec. 31, 2018
Segment Reporting Information [Line Items]
Restructuring and Asset Related Charges - Net		$ 55		$ 46	[1]	$ 60	[1]	$ 61	[1]	$ 228	[1]	$ 235		$ 101	[1]	$ 130	[1]	$ 270	$ 12	$ 222		$ 694
Integration and Separation Costs		$ 50		152	[1]	330	[1]	212	[1]	295	[1]	$ 253		249	[1]	195	[1]	255		744		992
Gain (Loss) on Disposition of Assets														$ 24
Loss on Extinguishment of Debt						$ (13)				$ (81)								0	0	(13)		(81)
Net exchange losses																		(23)	(364)	(99)	[2],[3]	(127)	[2],[3],[4],[5]
Significant items																				991		1,346
Sale of JV [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets								$ (24)
Hedging Program [Member]
Segment Reporting Information [Line Items]
Net exchange losses																		$ 91	$ (431)	(58)		94	[5]
Hedging Program [Member] | Argentine peso devaluation [Member]
Segment Reporting Information [Line Items]
Net exchange losses				$ (33)																(51)		(68)
Hedging Program [Member] | Tax Reform Foreign Currency Exchange Impact [Member]
Segment Reporting Information [Line Items]
Net exchange losses																$ (50)						(50)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Restructuring and Asset Related Charges - Net	[6]																			(222)		(694)
Integration and Separation Costs	[7]																			(632)
Business Combination, Fair Value Step-Up Of Acquired Inventory, Amount recognized in Cost of Goods sold	[8]																			(67)
Loss on Extinguishment of Debt	[9]																			(13)
Net exchange losses	[10]																			66		77
Integration costs	[7]																					(571)
Significant items																				(991)		(1,346)
Segment Reconciling Items [Member] | Seed [Member]
Segment Reporting Information [Line Items]
Restructuring and Asset Related Charges - Net	[6]																			(213)		(368)
Business Combination, Fair Value Step-Up Of Acquired Inventory, Amount recognized in Cost of Goods sold	[8]																			(67)
Significant items																				(304)		(399)
Segment Reconciling Items [Member] | Crop Protection [Member]
Segment Reporting Information [Line Items]
Restructuring and Asset Related Charges - Net	[6]																			(23)		(58)
Significant items																				(23)		(58)
Segment Reconciling Items [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Restructuring and Asset Related Charges - Net	[6]																			14		(268)
Integration and Separation Costs	[7]																			(632)
Loss on Extinguishment of Debt	[9]																			(13)
Integration costs	[7]																					(571)
Significant items																				(664)		(889)
Segment Reconciling Items [Member] | Sale of JV [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[11]																			(24)
Segment Reconciling Items [Member] | Sale of JV [Member] | Seed [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[11]																			(24)
Segment Reconciling Items [Member] | Asset sale [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[12]																					24
Segment Reconciling Items [Member] | Asset sale [Member] | Seed [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[12]																					24
Segment Reconciling Items [Member] | Deconsolidation of a subsidiary [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[13]																					(53)
Segment Reconciling Items [Member] | Deconsolidation of a subsidiary [Member] | Seed [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[13]																					(53)
Segment Reconciling Items [Member] | Other loss on sale [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[14]																					(2)
Segment Reconciling Items [Member] | Other loss on sale [Member] | Seed [Member]
Segment Reporting Information [Line Items]
Gain (Loss) on Disposition of Assets	[14]																					(2)
Segment Reconciling Items [Member] | Hedging Program [Member] | Argentine peso devaluation [Member]
Segment Reporting Information [Line Items]
Net exchange losses	[15]																			(33)
Segment Reconciling Items [Member] | Hedging Program [Member] | Argentine peso devaluation [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Net exchange losses	[15]																			$ (33)
Segment Reconciling Items [Member] | Hedging Program [Member] | Tax Reform Foreign Currency Exchange Impact [Member]
Segment Reporting Information [Line Items]
Net exchange losses	[16]																					(50)
Segment Reconciling Items [Member] | Hedging Program [Member] | Tax Reform Foreign Currency Exchange Impact [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Net exchange losses	[16]																					$ (50)

[1] Note 7 - Restructuring and Asset Related Charges - Net, Note 5 - Divestitures and Other Transactions, and Note 15 - Goodwill and Other Intangible Assets, for additional information related to integration and separation costs, restructuring and asset related charges - net, discontinued operations, and goodwill impairment charge, respectively.

[2] Includes a net $(51) million and $(68) million pre-tax exchange loss associated with the devaluation of the Argentine peso for the year ended December 31, 2019 and December 31, 2018, respectively.

[3] Includes a net $(51) million and $(68) million pre-tax exchange loss associated with the devaluation of the Argentine peso for the year ended December 31, 2019 and December 31, 2018, respectively.

[4] Includes a $(50) million foreign exchange loss for the year ended December 31, 2018 related to adjustments to foreign currency exchange contracts as a result of U.S. tax reform, which is included within significant items.

[5] Includes a $(50) million foreign exchange loss for the year ended December 31, 2018 related to adjustments to foreign currency exchange contracts as a result of U.S. tax reform.

[6] Includes Board approved restructuring plans and asset related charges, which includes other asset impairments. See Note 7 - Restructuring and Asset Related Charges - Net, for additional information.

[7] Integration and separation costs related to post-Merger integration and Business Separation activities.

[8] Includes charges related to the amortization on the inventory that was stepped up to fair value in connection with the Merger, recognized in cost of goods sold.

[9] Includes a loss related to the difference between the redemption price and the par value of the Make Whole Notes and Term Loan Facility, partially offset by the write-off of unamortized step-up related to the fair value step-up of EID’s debt.

[10] Excludes a $(33) million foreign exchange loss for the year ended December 31, 2019 associated with the devaluation of the Argentine peso and a $(50) million foreign exchange loss for the year ended December 31, 2018 related to adjustments to foreign currency exchange contracts as a result of U.S. tax reform, as they are included within significant items. See Note 9 - Supplementary Information, for additional information.

[11] Includes a loss recorded in other income (expense) - net related to Historical Dow’s sale of a joint venture related to synergy actions.

[12] Includes a gain recorded in other income (expense) - net related to an asset sale.

[13] Includes a loss recorded in other income (expense) - net related to the deconsolidation of a subsidiary.

[14] Includes a loss recorded in other income (expense) - net related to an asset sale.

[15] Includes a charge included in other income (expense) - net associated with remeasuring the company’s Argentine Peso net monetary assets, resulting from an unexpected August primary election result in Argentina.  Throughout the three months ended September 30, 2019, the Argentine Peso dropped approximately a third of its value against the US dollar and in September of 2019, the country’s central bank announced new restrictions on foreign currency transactions.

[16] Includes a foreign exchange loss recorded in other income (expense) - net related to adjustments to foreign currency exchange contracts as a result of U.S. tax reform.