Summary of Sundry Income (Expense) - Net (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Sundry income (expense) - net	$ 182		$ 301	$ 154	$ 369
Gain (Loss) on Extinguishment of Debt	63		0	149	44
Gain (Loss) Related to Litigation Settlement	0		205	6	205
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	220		0	220	(44)
Charges related to separation, distribution and tax matters agreements			0		(127)
Nonoperating Income (Expense)
Sundry income (expense) - net	182		301	154	369
Gain (Loss) on Extinguishment of Debt	(63)		0	(149)	(44)
Other Nonoperating Income (Expense)	21		9	26	45
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	(13)		0	(13)	(44)
Gain (Loss) on Disposition of Other Assets	2		26	7	33
Charges related to separation, distribution and tax matters agreements	0		0	0	(52)
Net periodic benefit cost	26		44	81	161
Foreign Currency Transaction Gain (Loss), before Tax	(24)		17	(42)	65
Breast Implant and Other Products Liability Claims [Member] | Nonoperating Income (Expense)
Loss Contingency Accrual, Period Increase (Decrease)	0		85	5	85
Rail Infrastructure | Nonoperating Income (Expense)
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	233		0	233	0
The Dow Chemical Company [Domain]
Sundry income (expense) - net	181		284	150	462
Gain (Loss) on Extinguishment of Debt	(63)		0	(149)	(44)
Other Nonoperating Income (Expense)	18		11	25	47
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	(13)		(5)	(13)	9
Gain (Loss) on Disposition of Other Assets	2		26	7	33
Net periodic benefit cost	26		44	81	161
Foreign Currency Transaction Gain (Loss), before Tax	(22)		3	(45)	51
The Dow Chemical Company [Domain] | Breast Implant and Other Products Liability Claims [Member]
Loss Contingency Accrual, Period Increase (Decrease)	0		85	5	85
The Dow Chemical Company [Domain] | Rail Infrastructure
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	233		0	233	0
Nova Ethylene Asset Matter [Member]
Gain (Loss) Related to Litigation Settlement		$ 18	186
Nova Ethylene Asset Matter [Member] | Nonoperating Income (Expense)
Gain (Loss) Related to Litigation Settlement	0		170	6	170
Nova Ethylene Asset Matter [Member] | The Dow Chemical Company [Domain]
Gain (Loss) Related to Litigation Settlement	0		170	6	170
Commercial Creditors Litigation [Member] | Nonoperating Income (Expense)
Loss Contingency Accrual, Period Increase (Decrease)	0		(50)	0	(50)
Commercial Creditors Litigation [Member] | The Dow Chemical Company [Domain]
Loss Contingency Accrual, Period Increase (Decrease)	$ 0		$ (50)	$ 0	$ (50)