Stockholders' Equity Reclassifications out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended															12 Months Ended
		Dec. 31, 2020	[1]	Sep. 30, 2020	Jun. 30, 2020	[2]	Mar. 31, 2020	[3],[4]	Dec. 31, 2019	[5]	Sep. 30, 2019	[6],[7]	Jun. 30, 2019	[8]	Mar. 31, 2019	[9]	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Tax Expense (Benefit)																	$ (81)	$ (46)	$ (31)
Income (loss) from continuing operations after income taxes		$ 99		$ (390)	$ 766		$ 281		$ (42)		$ (527)		$ 483		$ (184)		756	(270)	(6,775)
Derivative Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Tax Expense (Benefit)	[10]																(6)	(1)	1
Income (loss) from continuing operations after income taxes																	12	12	(5)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[11]																18	13	(6)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																	12	12	(5)
AOCI Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																	18	16	4
Pension Plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																	5	5	9
Pension Plan | Prior Service Benefit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[12],[13]																(1)	(1)	0
Pension Plan | Actuarial Losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[12],[13],[14]																4	2	6
Pension Plan | Curtailment (loss) gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[12],[13],[14]																0	0	7
Pension Plan | Accumulated Defined Benefit Plans Adjustment, Settlement Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[12],[13],[14]																3	4	(2)
Pension Plan | Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax																	6	5	11
Reclassification from AOCI, Current Period, Tax	[10]																(1)	0	(2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																	5	5	9
Other Benefit Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																	1	(1)	0
Other Benefit Plans | Prior Service Benefit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[12],[13]																0	0	0
Other Benefit Plans | Actuarial Losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[12],[13]																1	(1)	0
Other Benefit Plans | Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax																	1	(1)	0
Reclassification from AOCI, Current Period, Tax	[10]																0	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																	$ 1	$ (1)	$ 0

[1] Fourth quarter 2020 includes an after-tax benefit of $(182) million related to Swiss Tax Reform. See Note 10 - Income Taxes, to the Consolidated Financial Statements, for additional information.

[2] Second quarter 2020 includes an after-tax benefit of $(29) million due to an elective change in accounting method that alters the 2019 impact of the business separation on the 2017 Tax Cuts and Jobs Act's foreign tax provision. See Note 10 - Income Taxes, to the Consolidated Financial Statements for additional information.

[3] First quarter 2020 includes a $19 million after tax charge related to the impact of a state tax valuation allowance in the U.S. based on a change in judgment about the realizability of a deferred tax asset. See Note 10 - Income Taxes, to the Consolidated Financial Statements, for additional information.

[4] First quarter 2020 includes a loss of $(53) million recorded in other income - net related to the expected sale of the La Porte site, for which the company signed an agreement during the first quarter 2020.

[5] Fourth quarter 2019 includes a tax benefit of $(34) million related to the impact of the release of a tax valuation allowance recorded against the net deferred tax asset position of a Switzerland legal entity. See Note 10 - Income Taxes, to the Consolidated Financial Statements for additional information.

[6] Third quarter 2019 includes a $33 million charge included in other income (expense) - net associated with remeasuring the company’s Argentine Peso net monetary assets, resulting from an unexpected August primary election result in Argentina. 

[7] Third quarter 2019 includes a tax benefit of $(38) million related to Swiss Tax Reform. See Note 10 - Income Taxes, to the Consolidated Financial Statements for additional information.

[8] Includes a loss on early extinguishment of debt of $(13) million in the second quarter of 2019 related to the retirement of some of the company's debt. See Note 17 - Long-Term Debt and Available Credit Facilities, to the Consolidated Financial Statements for additional information.

[9] First quarter 2019 includes a $(24) million loss recorded in other income (expense) - net related to Historical Dow’s sale of a joint venture related to synergy actions.

[10] Reflected in benefit from income taxes from continuing operations.

[11] Reflected in cost of goods sold.

[12] Reflected in other income (expense) - net.

[13] These accumulated other comprehensive (loss) income components are included in the computation of net periodic benefit (credit) cost of the company's pension and other benefit plans. See Note 20 - Pension Plans and Other Post Employment Benefits, to the Consolidated Financial Statements, for additional information.

[14] A portion reflected in (Loss) income from discontinued operations after income taxes for the years ended December 31, 2019 and 2018.