Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Net external sales	$ 1,004,165	$ 821,175	$ 2,807,859	$ 2,770,000
Income (loss) from operations	266,602	142,517	695,884	459,120
Depreciation and amortization	40,728	38,424	116,294	109,601
Other (expense) income, net	(287)	1,222	3,137	3,676
Provision for (benefit from) income taxes	92,728	38,236	244,647	146,183
Capital expenditures	200,418	94,895	498,290	235,463
Olefins
Segment Reporting Information [Line Items]
Net external sales	679,339	539,785	1,885,525	1,944,775
Income (loss) from operations	237,239	124,452	585,958	409,550
Depreciation and amortization	26,515	27,070	76,415	74,903
Other (expense) income, net	728	806	5,889	2,764
Provision for (benefit from) income taxes	82,553	36,092	208,170	130,612
Capital expenditures	27,577	46,867	105,656	92,168
Vinyls
Segment Reporting Information [Line Items]
Net external sales	324,826	281,390	922,334	825,225
Income (loss) from operations	39,554	24,059	136,123	67,724
Depreciation and amortization	14,089	11,232	39,507	34,330
Other (expense) income, net	(742)	146	(1,687)	115
Provision for (benefit from) income taxes	10,710	6,556	44,120	18,989
Capital expenditures	172,565	47,001	391,864	139,836
Corporate and Other
Segment Reporting Information [Line Items]
Income (loss) from operations	(10,191)	(5,994)	(26,197)	(18,154)
Depreciation and amortization	124	122	372	368
Other (expense) income, net	(273)	270	(1,065)	797
Provision for (benefit from) income taxes	(535)	(4,412)	(7,643)	(3,418)
Capital expenditures	276	1,027	770	3,459
Polyethylene | Olefins
Segment Reporting Information [Line Items]
Net external sales	460,105	431,614	1,294,566	1,275,057
Ethylene, Styrene And Other | Olefins
Segment Reporting Information [Line Items]
Net external sales	219,234	108,171	590,959	669,718
PVC, Caustic Soda And Other | Vinyls
Segment Reporting Information [Line Items]
Net external sales	212,041	191,310	612,391	569,316
Building Products | Vinyls
Segment Reporting Information [Line Items]
Net external sales	112,785	90,080	309,943	255,909
Intersegment sales
Segment Reporting Information [Line Items]
Net external sales	85,857	77,162	231,718	248,838
Intersegment sales | Olefins
Segment Reporting Information [Line Items]
Net external sales	85,454	76,771	230,607	247,671
Intersegment sales | Vinyls
Segment Reporting Information [Line Items]
Net external sales	$ 403	$ 391	$ 1,111	$ 1,167