Segment Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,932	$ 2,025
Income (loss) from operations	136	134
Depreciation and amortization	190	171
Other income, net	11	9
Provision for (benefit from) income taxes	(41)	31
Capital expenditures	164	203
Operating Segments [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	427	459
Income (loss) from operations	62	37
Depreciation and amortization	35	35
Other income, net	1	2
Provision for (benefit from) income taxes	41	9
Capital expenditures	27	25
Operating Segments [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,505	1,566
Income (loss) from operations	73	101
Depreciation and amortization	153	134
Other income, net	6	4
Provision for (benefit from) income taxes	(78)	23
Capital expenditures	136	177
Operating Segments [Member] | Polyethylene [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	310	337
Operating Segments [Member] | Styrene, Feedstock And Other [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	117	122
Operating Segments [Member] | PVC, Caustic Soda And Other [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,213	1,307
Operating Segments [Member] | Building Products [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	292	259
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	1	(4)
Depreciation and amortization	2	2
Other income, net	4	3
Provision for (benefit from) income taxes	(4)	(1)
Capital expenditures	1	1
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Net sales	68	92
Intersegment sales [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	68	92
Intersegment sales [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	$ 0	$ 0