Quaterly Financial Data Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Net Sales	$ 3,207		$ 1,863		$ 5,191		$ 3,956		$ 2,983		$ 1,911		$ 5,556		$ 3,396		$ 14,217	$ 13,846	$ 14,287
Cost of Goods Sold	2,112		1,297		2,829		2,269		1,968	[1]	1,349	[1]	3,047	[1]	2,211	[1]	8,507	8,575	9,948
Restructuring and asset related charges- net	37	[2]	49	[2]	179	[2]	70	[2]	55	[2]	46	[2]	60	[2]	61	[2]	335	222	694
Integration and Separation Costs									50	[2]	152	[2]	330	[2]	212	[2]	0	744	992
Goodwill Impairment Charge																	0	0	4,503
(Loss) income from continuing operations after income taxes	99	[3]	(390)		766	[4]	281	[5],[6]	(42)	[7]	(527)	[8],[9]	483	[10]	(184)	[11]	756	(270)	(6,775)
Net (loss) income attributable to Company	$ 41	[2]	$ (392)	[2]	$ 760	[2]	$ 272	[2]	$ (21)	[2]	$ (494)	[2]	$ (608)	[2]	$ 164	[2]	$ 681	$ (959)	$ (5,065)
(Loss) earnings per common share, continuing operations - basic	$ 0.13	[12]	$ (0.52)	[12]	$ 1.01	[12]	$ 0.36	[12]	$ (0.06)	[12]	$ (0.69)	[12]	$ 0.63	[12]	$ (0.26)	[12]	$ 0.98	$ (0.38)	$ (9.08)
(Loss) earnings per common share, continuing operations - diluted	$ 0.13	[12]	$ (0.52)	[12]	$ 1.01	[12]	$ 0.36	[12]	$ (0.06)	[12]	$ (0.69)	[12]	$ 0.63	[12]	$ (0.26)	[12]	$ 0.98	$ (0.38)	$ (9.08)

[1] Includes charges of $205 million, $52 million, and $15 million for the first quarter 2019, second quarter 2019, and third quarter 2019, respectively, related to the amortization of inventory step-up as a result of the Merger.

[2] See Note 2 - Summary of Significant Accounting Polices, Note 7 - Restructuring and Asset Related Charges - Net, Note 5 - Divestitures and Other Transactions, and Note 15 - Goodwill and Other Intangible Assets, to the Consolidated Financial Statements for additional information related to integration and separation costs, restructuring and asset related charges - net, and discontinued operations, respectively.

[3] 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.

[4] 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.

[5] 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.

[6] 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.

[7] 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.

[8] 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. 

[9] 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.

[10] 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.

[11] 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.

[12] Earnings per share for the year may not equal the sum of quarterly earnings per share due to rounding and the changes in average share calculations.