Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Net external sales	$ 1,253,227	$ 1,004,165	$ 3,279,479	$ 2,807,859
Income (loss) from operations	306,761	266,602	821,604	695,884
Depreciation and amortization	53,920	40,728	148,394	116,294
Other (expense) income, net	(2,670)	(287)	4,440	3,137
Provision for (benefit from) income taxes	124,449	92,728	300,231	244,647
Capital expenditures	94,271	200,418	311,183	498,290
Olefins
Segment Reporting Information [Line Items]
Net external sales	703,097	679,339	2,124,948	1,885,525
Income (loss) from operations	259,277	237,239	770,267	585,958
Depreciation and amortization	26,443	26,515	79,811	76,415
Other (expense) income, net	1,609	728	4,262	5,889
Provision for (benefit from) income taxes	105,030	82,553	282,082	208,170
Capital expenditures	48,519	27,577	121,041	105,656
Vinyls
Segment Reporting Information [Line Items]
Net external sales	550,130	324,826	1,154,531	922,334
Income (loss) from operations	59,445	39,554	76,460	136,123
Depreciation and amortization	27,336	14,089	68,127	39,507
Other (expense) income, net	1,189	(742)	942	(1,687)
Provision for (benefit from) income taxes	21,761	10,710	22,121	44,120
Capital expenditures	44,067	172,565	187,449	391,864
Corporate and Other
Segment Reporting Information [Line Items]
Income (loss) from operations	(11,961)	(10,191)	(25,123)	(26,197)
Depreciation and amortization	141	124	456	372
Other (expense) income, net	(5,468)	(273)	(764)	(1,065)
Provision for (benefit from) income taxes	(2,342)	(535)	(3,972)	(7,643)
Capital expenditures	1,685	276	2,693	770
Polyethylene | Olefins
Segment Reporting Information [Line Items]
Net external sales	498,450	460,105	1,461,097	1,294,566
Ethylene, Styrene And Other | Olefins
Segment Reporting Information [Line Items]
Net external sales	204,647	219,234	663,851	590,959
PVC, Caustic Soda And Other | Vinyls
Segment Reporting Information [Line Items]
Net external sales	416,771	212,041	776,060	612,391
Building Products | Vinyls
Segment Reporting Information [Line Items]
Net external sales	133,359	112,785	378,471	309,943
Intersegment sales
Segment Reporting Information [Line Items]
Net external sales	26,873	85,857	119,182	231,718
Intersegment sales | Olefins
Segment Reporting Information [Line Items]
Net external sales	26,518	85,454	118,153	230,607
Intersegment sales | Vinyls
Segment Reporting Information [Line Items]
Net external sales	$ 355	$ 403	$ 1,029	$ 1,111