Summary of Sundry Income (Expense) - Net (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Gain (Loss) on Extinguishment of Debt	$ (44)		$ (44)
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	(44)	$ 0	(44)	$ 20
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net		(20)	0	20
Charges related to separation, distribution and tax matters agreements	127		127
Other Operating Income (Expense) [Member]
Charges related to separation, distribution and tax matters agreements	52
Dow Silicones Corporation [Member]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net				(20)
Corporate Segment [Member]
Gain (Loss) on Extinguishment of Debt	(44)		(44)
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	(44)	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	127		127
Performance Materials & Coatings [Member]
Gain (Loss) on Extinguishment of Debt	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		(20)		(20)
Charges related to separation, distribution and tax matters agreements	0		0
Industrial Intermediates & Infrastructure [Member]
Gain (Loss) on Extinguishment of Debt	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	109	(14)	178	40
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	(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]
Sundry income (expense) - net	$ (1)	$ (14)	68	$ 40
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)

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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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- Definition

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

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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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The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

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