Stockholders' Equity Reclassifications out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended																4 Months Ended	8 Months Ended	12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017	Aug. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of Goods Sold		$ 1,968		$ 1,349	[1]	$ 3,047	[1]	$ 2,211	[1]	$ 2,024	[1]	$ 1,485	[1]	$ 3,687	[1]	$ 2,752	[1]	$ 2,915	$ 3,409	$ 8,575	$ 9,948
Income Tax Expense (Benefit)																		(2,221)	(395)	(46)	(31)
(Loss) income from continuing operations after income taxes		$ (42)	[2]	$ (527)	[3],[4]	$ 483	[5]	$ (184)	[6]	$ (1,070)	[5],[6],[7]	$ (5,642)	[7],[8]	$ 375	[7],[9]	$ (438)	[7],[10]	1,760	358	(270)	(6,775)
Derivative Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of Goods Sold	[11]																	0	(21)	13	(6)
Income Tax Expense (Benefit)	[12]																	0	8	(1)	1
(Loss) income from continuing operations after income taxes																		0	(13)	12	(5)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																		0	(13)	12	(5)
Gain (Loss) on Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[13]																	0	(1)	0	0
Reclassification from AOCI, Current Period, Tax	[12]																	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																		0	(1)	0	0
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																		(4)	321	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																		(4)	325	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	[13],[14]																	0	(3)	(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	[13],[14],[15]																	(5)	506	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	[13],[14],[15]																	0	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	[13],[14],[15]																	0	0	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																		(5)	503	5	11
Reclassification from AOCI, Current Period, Tax	[12]																	1	(178)	0	(2)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																		(4)	325	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																		0	10	(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	[13],[14]																	0	(46)	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	[13],[14]																	0	61	(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																		0	15	(1)	0
Reclassification from AOCI, Current Period, Tax	[12]																	0	(5)	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																		$ 0	$ 10	$ (1)	$ 0

[1] Includes charges of $(639) million, $(676) million, $(109) million, and $(130) million for the first quarter 2018, second quarter 2018, third quarter 2018, and fourth quarter 2018, respectively, and $(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] 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, for additional information.

[3] 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. 

[4] Third quarter 2019 includes a tax benefit of $38 million related to Swiss Tax Reform. See Note 10 - Income Taxes, for additional information.

[5] Includes a loss on early extinguishment of debt of $(13) million in the second quarter of 2019 and $(81) million in the fourth quarter 2018 related to the retirement of some of the company's debt. See Note 17 - Short-Term Borrowings, Long-Term Debt and Available Credit Facilities, for additional information.

[6] 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. Fourth quarter 2018 includes a $(53) million loss recorded in other income (expense) - net related to the deconsolidation of a subsidiary.

[7] Includes tax (charges) benefits of $(64) million, $(7) million, $16 million, and $(274) million in the first quarter 2018, second quarter 2018, third quarter 2018, and fourth quarter 2018, respectively, related to The Act. See Note 10 - Income Taxes, for additional information.

[8] Includes a tax charge of $(75) million in the third quarter 2018 related to the establishment of a full valuation allowance against the net deferred tax asset position of a legal entity in Brazil, a tax charge of $(25) million related to an internal legal entity restructuring associated with the Business Separations, and a tax benefit of $114 million related to the company's discretionary pension contribution in 2018 which was deducted on a 2017 tax return. See Note 10 - Income Taxes, for additional information.

[9] Second quarter 2018 includes a $24 million gain recorded in other income (expense) - net related to an asset sale.

[10] First quarter 2018 includes a $(50) million foreign exchange loss related to adjustments to foreign currency exchange contracts as a result of U.S. tax reform.

[11] Cost of goods sold.

[12] Benefit from income taxes from continuing operations.

[13] Other income (expense) - net.

[14] 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, for additional information.

[15] (Loss) income from discontinued operations after income taxes.