Summary of Sundry Income (Expense) - Net (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Sundry income (expense) - net	$ 301	$ (3)	$ 369	$ 37
Gain (Loss) Related to Litigation Settlement	205		205
Gain (Loss) on Extinguishment of Debt	0	(6)	(44)	(6)
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	0	(44)	20
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net		0	0	20
Charges related to separation, distribution and tax matters agreements	0		127
Dow Silicones Corporation [Member]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net				(20)
Packaging & Specialty Plastics [Member]
Gain (Loss) Related to Litigation Settlement	170		170
Gain (Loss) on Extinguishment of Debt	0	0	0	0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	0	0	0
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net		0		0
Charges related to separation, distribution and tax matters agreements	0		0
Corporate Segment [Member]
Gain (Loss) Related to Litigation Settlement	35		35
Gain (Loss) on Extinguishment of Debt	0	(6)	(44)	(6)
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	0	(44)	0
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net		0		0
Charges related to separation, distribution and tax matters agreements	0		127
Performance Materials & Coatings [Member]
Gain (Loss) Related to Litigation Settlement	0		0
Gain (Loss) on Extinguishment of Debt	0	0	0	0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	0	0	0
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net		0		(20)
Charges related to separation, distribution and tax matters agreements	0		0
Industrial Intermediates & Infrastructure [Member]
Gain (Loss) Related to Litigation Settlement	0		0
Gain (Loss) on Extinguishment of Debt	0	0	0	0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	0	0	20
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net		0		0
Charges related to separation, distribution and tax matters agreements	0		0
The Dow Chemical Company [Domain]
Sundry income (expense) - net	284	(3)	462	37
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net			0	(20)
The Dow Chemical Company [Domain] \| Corporate Segment [Member]
Gain (Loss) on Extinguishment of Debt		$ (6)	(44)
The Dow Chemical Company [Domain] \| Corporate Segment [Member] \| Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			14
The Dow Chemical Company [Domain] \| Performance Materials & Coatings [Member] \| Dow Silicones Corporation [Member]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net				(20)
The Dow Chemical Company [Domain] \| Industrial Intermediates & Infrastructure [Member] \| Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] \| MEGlobal [Member]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal				$ 20
Dow Inc. [Member] \| Other Operating Income (Expense) [Member]
Charges related to separation, distribution and tax matters agreements			(52)
Dow Inc. [Member] \| Corporate Segment [Member] \| Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			(58)
Nova Ethylene Asset Matter [Member]
Gain (Loss) Related to Litigation Settlement	186
Nova Ethylene Asset Matter [Member] \| Packaging & Specialty Plastics [Member]
Gain (Loss) Related to Litigation Settlement	170
Breast Implant and Other Products Liability Claims [Member] \| Corporate Segment [Member]
Gain (Loss) Related to Litigation Settlement	85
Commercial Creditor Issues [Member] \| Corporate Segment [Member]
Gain (Loss) Related to Litigation Settlement	(50)
Indemnification Asset	$ 37		$ 37

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In a business combination achieved in stages, this element represents the amount of net gain (loss) recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

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Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

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Amount of gain (loss) recognized in settlement of litigation and insurance claims. Excludes claims within an insurance entity's normal claims settlement process.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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