Segment Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Net sales	$ 1,709	$ 2,144	$ 3,641	$ 4,169
Income (loss) from operations	36	194	172	328
Depreciation and amortization	191	176	381	347
Other income, net	9	2	20	11
Provision for (benefit from) income taxes	(19)	39	(60)	70
Capital expenditures	127	208	291	411
Operating Segments [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	361	477	788	936
Income (loss) from operations	25	82	87	119
Depreciation and amortization	35	36	70	71
Other income, net	0	1	1	3
Provision for (benefit from) income taxes	(4)	18	37	27
Capital expenditures	17	37	44	62
Operating Segments [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,348	1,667	2,853	3,233
Income (loss) from operations	20	129	93	230
Depreciation and amortization	154	138	307	272
Other income, net	8	2	14	6
Provision for (benefit from) income taxes	(18)	22	(96)	45
Capital expenditures	108	169	244	346
Operating Segments [Member] | Polyethylene [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	302	345	612	682
Operating Segments [Member] | Styrene, Feedstock And Other [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	59	132	176	254
Operating Segments [Member] | PVC, Caustic Soda And Other [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,004	1,319	2,217	2,626
Operating Segments [Member] | Building Products [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	344	348	636	607
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(9)	(17)	(8)	(21)
Depreciation and amortization	2	2	4	4
Other income, net	1	(1)	5	2
Provision for (benefit from) income taxes	3	(1)	(1)	(2)
Capital expenditures	2	2	3	3
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Net sales	37	75	105	167
Intersegment sales [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	36	74	104	166
Intersegment sales [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	$ 1	$ 1	$ 1	$ 1