Summary of Sundry Income (Expense) - Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Gain (Loss) on Extinguishment of Debt	$ 102	$ 0	$ 102	$ 86
Charges related to separation, distribution and tax matters agreements	(5)		(5)
Gain (Loss) Related to Litigation Settlement		6		6
Sundry income (expense) - net	(3)	53	125	(28)
Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	86	27	161	54
Foreign Currency Transaction Gain (Loss), before Tax	(8)	(2)	(16)	(18)
Gain (Loss) on Extinguishment of Debt	(102)	0	(102)	(86)
Gain (Loss) on Disposition of Other Assets	14	(4)	62	5
Charges related to separation, distribution and tax matters agreements	(5)	0	(5)	0
Other Nonoperating Income (Expense)	12	26	25	11
Sundry income (expense) - net	(3)	53	125	(28)
Nonoperating Income (Expense) | Nova Ethylene Asset Matter [Member]
Gain (Loss) Related to Litigation Settlement	0	6	0	6
The Dow Chemical Company
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	86	27	161	54
Foreign Currency Transaction Gain (Loss), before Tax	(4)	(6)	(16)	(23)
Gain (Loss) on Extinguishment of Debt	(102)	0	(102)	(86)
Gain (Loss) on Disposition of Other Assets	14	(4)	62	5
Other Nonoperating Income (Expense)	12	28	20	13
Sundry income (expense) - net	6	51	125	(31)
The Dow Chemical Company | Nova Ethylene Asset Matter [Member]
Gain (Loss) Related to Litigation Settlement	$ 0	$ 6	$ 0	$ 6