Segment Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Net sales	$ 3,055	$ 1,898	$ 8,271	$ 5,539
Income (loss) from operations	861	79	1,927	251
Depreciation and amortization	203	196	600	577
Other income, net	13	12	35	32
Provision for (benefit from) income taxes	193	(15)	423	(75)
Capital expenditures	144	112	414	403
Operating Segments [Member] | Olefins
Segment Reporting Information [Line Items]
Net sales	707	369	1,915	1,157
Income (loss) from operations	281	51	738	138
Depreciation and amortization	36	34	109	104
Other income, net	0	1	2	2
Provision for (benefit from) income taxes	66	4	170	41
Capital expenditures	19	16	66	60
Operating Segments [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	2,348	1,529	6,356	4,382
Income (loss) from operations	601	42	1,236	135
Depreciation and amortization	166	160	486	467
Other income, net	10	7	27	21
Provision for (benefit from) income taxes	141	(25)	279	(121)
Capital expenditures	124	94	346	338
Operating Segments [Member] | Polyethylene [Member] | Olefins
Segment Reporting Information [Line Items]
Net sales	559	302	1,488	914
Operating Segments [Member] | Styrene, Feedstock And Other [Member] | Olefins
Segment Reporting Information [Line Items]
Net sales	148	67	427	243
Operating Segments [Member] | PVC, Caustic Soda And Other [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	1,834	1,116	4,950	3,333
Operating Segments [Member] | Building Products [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	514	413	1,406	1,049
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(21)	(14)	(47)	(22)
Depreciation and amortization	1	2	5	6
Other income, net	3	4	6	9
Provision for (benefit from) income taxes	(14)	6	(26)	5
Capital expenditures	1	2	2	5
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Net sales	163	79	447	184
Intersegment sales [Member] | Olefins
Segment Reporting Information [Line Items]
Net sales	163	79	447	183
Intersegment sales [Member] | Vinyls
Segment Reporting Information [Line Items]
Net sales	$ 0	$ 0	$ 0	$ 1