Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=120320667&loc=SL49117168-202975

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillForeignCurrencyTranslationGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13854-109267

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266

+ Details

Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease), classified as other, of an asset representing the future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillOtherIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_GoodwillRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillWrittenOffRelatedToSaleOfBusinessUnit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=dow_RailInfrastructureOperationsAndAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=dow_MarineAndTerminalOperationsAndAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=dow_PackagingSpecialtyPlasticsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=dow_IndustrialIntermediatesInfrastructureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=dow_PerformanceMaterialsCoatingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

GOODWILL AND OTHER INTANGIBLE ASSETS (Schedule of Goodwill) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Net goodwill, beginning balance		$ 8,796	$ 9,846
Foreign currency impact		122	(10)
Goodwill, Impairment Loss			(1,039)
Goodwill, Other Increase (Decrease)			(1)
Net goodwill, ending balance	$ 8,796	8,908	8,796
Rail Infrastructure Operations and Assets [Member]
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		(2)
Marine and Terminal Operations and Assets
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		(8)
Packaging & Specialty Plastics [Member]
Goodwill [Roll Forward]
Net goodwill, beginning balance		5,109	5,101
Foreign currency impact		12	8
Goodwill, Impairment Loss			0
Goodwill, Other Increase (Decrease)			0
Net goodwill, ending balance	5,109	5,115	5,109
Packaging & Specialty Plastics [Member] \| Rail Infrastructure Operations and Assets [Member]
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		(2)
Packaging & Specialty Plastics [Member] \| Marine and Terminal Operations and Assets
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		(4)
Industrial Intermediates & Infrastructure [Member]
Goodwill [Roll Forward]
Net goodwill, beginning balance		1,100	1,095
Foreign currency impact		4	6
Goodwill, Impairment Loss			0
Goodwill, Other Increase (Decrease)			(1)
Net goodwill, ending balance	1,100	1,100	1,100
Industrial Intermediates & Infrastructure [Member] \| Rail Infrastructure Operations and Assets [Member]
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		0
Industrial Intermediates & Infrastructure [Member] \| Marine and Terminal Operations and Assets
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		(4)
Performance Materials & Coatings [Member]
Goodwill [Roll Forward]
Net goodwill, beginning balance		2,587	3,650
Foreign currency impact		106	(24)
Goodwill, Impairment Loss	(1,039)		(1,039)
Goodwill, Other Increase (Decrease)			0
Net goodwill, ending balance	$ 2,587	2,693	$ 2,587
Performance Materials & Coatings [Member] \| Rail Infrastructure Operations and Assets [Member]
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		0
Performance Materials & Coatings [Member] \| Marine and Terminal Operations and Assets
Goodwill [Roll Forward]
Goodwill, Written off Related to Sale of Business Unit		$ 0