Segment Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,898	$ 2,066	$ 5,539	$ 6,235
Income (loss) from operations	79	226	251	554
Depreciation and amortization	196	178	577	525
Other income, net	12	21	32	32
Provision for (benefit from) income taxes	(15)	50	(75)	120
Capital expenditures	112	193	403	604
Operating Segments [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	369	448	1,157	1,384
Income (loss) from operations	51	92	138	211
Depreciation and amortization	34	35	104	106
Other income, net	1	1	2	4
Provision for (benefit from) income taxes	4	18	41	45
Capital expenditures	16	25	60	87
Operating Segments [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	1,529	1,618	4,382	4,851
Income (loss) from operations	42	153	135	383
Depreciation and amortization	160	141	467	413
Other income, net	7	12	21	18
Provision for (benefit from) income taxes	(25)	31	(121)	76
Capital expenditures	94	165	338	511
Operating Segments [Member] | Polyethylene [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	302	315	914	997
Operating Segments [Member] | Styrene, Feedstock And Other [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	67	133	243	387
Operating Segments [Member] | PVC, Caustic Soda And Other [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	1,116	1,253	3,333	3,879
Operating Segments [Member] | Building Products [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	413	365	1,049	972
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(14)	(19)	(22)	(40)
Depreciation and amortization	2	2	6	6
Other income, net	4	8	9	10
Provision for (benefit from) income taxes	6	1	5	(1)
Capital expenditures	2	3	5	6
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Net sales	79	72	184	239
Intersegment sales [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	79	72	183	238
Intersegment sales [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	$ 0	$ 0	$ 1	$ 1