Segment Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net sales	$ 2,859	$ 1,709	$ 5,216	$ 3,641
Income (loss) from operations	720	36	1,066	172
Depreciation and amortization	202	191	397	381
Other income, net	10	9	22	20
Provision for (benefit from) income taxes	158	(19)	230	(60)
Capital expenditures	129	127	270	291
Operating Segments [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	671	361	1,208	788
Income (loss) from operations	277	25	457	87
Depreciation and amortization	37	35	73	70
Other income, net	2	0	2	1
Provision for (benefit from) income taxes	63	(4)	104	37
Capital expenditures	24	17	47	44
Operating Segments [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	2,188	1,348	4,008	2,853
Income (loss) from operations	435	20	635	93
Depreciation and amortization	163	154	320	307
Other income, net	7	8	17	14
Provision for (benefit from) income taxes	96	(18)	138	(96)
Capital expenditures	104	108	222	244
Operating Segments [Member] | Polyethylene [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	515	302	929	612
Operating Segments [Member] | Styrene, Feedstock And Other [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	156	59	279	176
Operating Segments [Member] | PVC, Caustic Soda And Other [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	1,708	1,004	3,116	2,217
Operating Segments [Member] | Building Products [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	480	344	892	636
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	8	(9)	(26)	(8)
Depreciation and amortization	2	2	4	4
Other income, net	1	1	3	5
Provision for (benefit from) income taxes	(1)	3	(12)	(1)
Capital expenditures	1	2	1	3
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Net sales	134	37	284	105
Intersegment sales [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	134	36	284	104
Intersegment sales [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	$ 0	$ 1	$ 0	$ 1