Summary of Sundry Income (Expense) - Net (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gain (Loss) on Extinguishment of Debt	$ 472	$ (63)	$ 574	$ 149
Charges related to separation, distribution and tax matters agreements	0		(5)
Sundry income (expense) - net	(350)	182	(225)	154
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		220		220
Nova Ethylene Asset Matter [Member]
Gain (Loss) Related to Litigation Settlement		0		6
Luxi Chemical Group Breach of Contract Matter [Member]
Gain (Loss) Related to Litigation Settlement	54		54
Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	86	26	247	81
Foreign Currency Transaction Gain (Loss), before Tax	(5)	(24)	(21)	(42)
Gain (Loss) on Extinguishment of Debt	(472)	(63)	(574)	(149)
Gain (Loss) on Disposition of Other Assets	12	2	74	7
Charges related to separation, distribution and tax matters agreements	0	0	(5)	0
Other Nonoperating Income (Expense)	(25)	21	0	26
Sundry income (expense) - net	(350)	182	(225)	154
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	(13)	0	(13)
Nonoperating Income (Expense) \| Rail Infrastructure
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	233	0	233
Nonoperating Income (Expense) \| Nova Ethylene Asset Matter [Member]
Gain (Loss) Related to Litigation Settlement	0	0	0	6
Nonoperating Income (Expense) \| Luxi Chemical Group Breach of Contract Matter [Member]
Gain (Loss) Related to Litigation Settlement	54	0	54	0
Breast Implant and Other Products Liability Claims [Member] \| Nonoperating Income (Expense)
Loss Contingency Accrual, Period Increase (Decrease)	0	0	0	5
The Dow Chemical Company
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	86	26	247	81
Foreign Currency Transaction Gain (Loss), before Tax	(8)	(22)	(24)	(45)
Gain (Loss) on Extinguishment of Debt	(472)	(63)	(574)	(149)
Gain (Loss) on Disposition of Other Assets	12	2	74	7
Other Nonoperating Income (Expense)	(28)	18	(8)	25
Sundry income (expense) - net	(356)	181	(231)	150
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	(13)	0	(13)
The Dow Chemical Company \| Rail Infrastructure
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	0	233	0	233
The Dow Chemical Company \| Nova Ethylene Asset Matter [Member]
Gain (Loss) Related to Litigation Settlement	0	0	0	6
The Dow Chemical Company \| Nonoperating Income (Expense) \| Luxi Chemical Group Breach of Contract Matter [Member]
Gain (Loss) Related to Litigation Settlement	54	0	54	0
The Dow Chemical Company \| Breast Implant and Other Products Liability Claims [Member]
Loss Contingency Accrual, Period Increase (Decrease)	$ 0	$ 0	$ 0	$ 5

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