ACCUMULATED OTHER COMPREHENSIVE LOSS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			$ 34	$ 27
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	$ (254)
Union Carbide Corporation's stockholder's equity	1,627	$ 1,831	1,627	1,831	$ 1,368	$ 1,798
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Union Carbide Corporation's stockholder's equity	(1,572)	(1,293)	(1,572)	(1,293)	(1,352)	(1,320)
Cumulative translation adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			1	3
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	0
Union Carbide Corporation's stockholder's equity	(58)	(59)	(58)	(59)	(59)	(62)
Pension and other postretirement benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			33	24
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	(254)
Union Carbide Corporation's stockholder's equity	(1,514)	(1,234)	(1,514)	(1,234)	$ (1,293)	$ (1,258)
Other Comprehensive Income (Loss), Tax	4	8	10	16
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	18	15	34	27
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cumulative translation adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	1	3	1	3
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension and other postretirement benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	21	20	43	40
Reclassification from AOCI, Current Period, Tax	(4)	(8)	(10)	(16)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 17	$ 12	$ 33	$ 24