BUSINESS SEPARATION (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Feb. 15, 2019
Dow International Holdings Company [Member]
Related Party Transaction [Line Items]
Common Stock, Related Company		1,067
Ownership Interest Percentage, Related Company	4.40%	11.90%
The Dow Chemical Company [Member]
Related Party Transaction [Line Items]
Dividends, Paid-in-kind	$ 71
The Dow Chemical Company [Member] \| Dow International Holdings Company [Member]
Related Party Transaction [Line Items]
Ownership Interest Percentage, Related Company		88.10%
Dividends, Common Stock, Stock	$ 401

Common Stock, Related Company

No definition available.

Name:	ucc_CommonStockRelatedCompany
Namespace Prefix:	ucc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Ownership Interest Percentage, Related Company

+ References

No definition available.

+ Details

Name:	ucc_OwnershipInterestPercentageRelatedCompany
Namespace Prefix:	ucc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of paid and unpaid common stock dividends declared with the form of settlement in stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

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

- Definition

Amount of paid and unpaid paid-in-kind dividends (PIK) declared for classes of stock, for example, but not limited to, common and preferred.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=ucc_DowInternationalHoldingsCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=ucc_DowChemicalCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis=ucc_DowChemicalCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: