Cover Page	3 Months Ended
	Mar. 31, 2021 shares
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	1-1463
Entity Registrant Name	Union Carbide Corporation
Entity Incorporation, State or Country Code	NY
Entity Tax Identification Number	13-1421730
Entity Address, Address Line One	7501 STATE HIGHWAY 185 NORTH
Entity Address, City or Town	SEADRIFT
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77983
City Area Code	361
Local Phone Number	553-2997
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	935.51
Entity Central Index Key	0000100790
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Title of 12(b) Security	None