Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accum. Other Comp Loss
Beginning balance at Dec. 31, 2017			$ 138	$ 2,582	$ (1,352)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Other			0
Stockholders' Equity, Period Increase (Decrease) | Adjustments for New Accounting Pronouncement [Member]				254	(254)
Net income attributable to Union Carbide Corporation	$ 1,055			1,055
Dividends declared				(553)
Stockholders' Equity, Other				0
Other Comprehensive Income (Loss), Net of Tax	45				45
Ending balance at Dec. 31, 2018	1,915	$ 0	138	3,338	(1,561)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Other			3
Stockholders' Equity, Period Increase (Decrease) | Adjustments for New Accounting Pronouncement [Member]				0	0
Net income attributable to Union Carbide Corporation	627			627
Dividends declared				(1,042)
Stockholders' Equity, Other				(1)
Other Comprehensive Income (Loss), Net of Tax	(104)				(104)
Ending balance at Dec. 31, 2019	1,398	0	141	2,922	(1,665)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Other			0
Stockholders' Equity, Period Increase (Decrease) | Adjustments for New Accounting Pronouncement [Member]				0	0
Net income attributable to Union Carbide Corporation	427			427
Dividends declared				(362)
Stockholders' Equity, Other				0
Other Comprehensive Income (Loss), Net of Tax	(105)				(105)
Ending balance at Dec. 31, 2020	$ 1,358	$ 0	$ 141	$ 2,987	$ (1,770)