Segment and Geographic Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net sales	$ 1,883	$ 2,066	$ 2,144	$ 2,025	$ 1,995	$ 2,255	$ 2,235	$ 2,150	$ 8,118	$ 8,635	$ 8,041
Income from operations	$ 102	$ 226	$ 194	$ 134	$ 207	$ 396	$ 404	$ 401	656	1,408	1,225
Depreciation and amortization									713	641	601
Other income, net									38	52	15
Provision for (benefit from) income taxes									108	300	(258)
Payments to Acquire Property, Plant, and Equipment									787	702	577
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									8,118	8,635	8,041
Operating Segments [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales									1,782	2,019	2,051
Income from operations									260	573	655
Depreciation and amortization									142	138	145
Other income, net									5	4	3
Provision for (benefit from) income taxes									60	128	63
Payments to Acquire Property, Plant, and Equipment									117	110	97
Operating Segments [Member] | Olefins [Member] | Polyethylene [Member]
Segment Reporting Information [Line Items]
Net sales									1,301	1,519	1,518
Operating Segments [Member] | Olefins [Member] | Styrene, Feedstock And Other [Member]
Segment Reporting Information [Line Items]
Net sales									481	500	533
Operating Segments [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales									6,336	6,616	5,990
Income from operations									451	913	639
Depreciation and amortization									563	491	449
Other income, net									18	35	7
Provision for (benefit from) income taxes									40	212	(302)
Payments to Acquire Property, Plant, and Equipment									664	585	459
Operating Segments [Member] | Vinyls [Member] | PVC, Caustic Soda And Other [Member]
Segment Reporting Information [Line Items]
Net sales									5,068	5,359	4,769
Operating Segments [Member] | Vinyls [Member] | Building Products [Member]
Segment Reporting Information [Line Items]
Net sales									1,268	1,257	1,221
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Income from operations									(55)	(78)	(69)
Depreciation and amortization									8	12	7
Other income, net									15	13	5
Provision for (benefit from) income taxes									8	(40)	(19)
Payments to Acquire Property, Plant, and Equipment									6	7	21
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales									325	502	394
Intersegment Eliminations [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales									324	500	393
Intersegment Eliminations [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales									$ 1	$ 2	$ 1