Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Net external sales	$ 1,185,002	$ 998,576	$ 2,288,533	$ 2,026,252
Income (loss) from operations	295,374	266,788	524,654	514,843
Depreciation and amortization	60,340	48,502	118,981	94,474
Other income (expense), net	22,058	4,601	31,154	7,110
Provision for (benefit from) income taxes	98,413	92,407	176,791	175,782
Capital expenditures	108,110	106,171	203,933	216,912
Olefins
Segment Reporting Information [Line Items]
Net external sales	620,878	699,053	1,203,955	1,421,851
Income (loss) from operations	220,938	238,657	412,041	510,990
Depreciation and amortization	27,623	26,721	54,562	53,368
Other income (expense), net	(104)	1,199	2,448	2,653
Provision for (benefit from) income taxes	74,212	83,502	140,669	177,052
Capital expenditures	81,534	43,448	136,835	72,522
Vinyls
Segment Reporting Information [Line Items]
Net external sales	564,124	299,523	1,084,578	604,401
Income (loss) from operations	87,966	38,129	135,052	17,015
Depreciation and amortization	32,599	21,623	64,183	40,791
Other income (expense), net	1,413	(213)	6,916	(247)
Provision for (benefit from) income taxes	26,653	10,430	39,458	360
Capital expenditures	24,569	62,262	61,425	143,382
Corporate and Other
Segment Reporting Information [Line Items]
Income (loss) from operations	(13,530)	(9,998)	(22,439)	(13,162)
Depreciation and amortization	118	158	236	315
Other income (expense), net	20,749	3,615	21,790	4,704
Provision for (benefit from) income taxes	(2,452)	(1,525)	(3,336)	(1,630)
Capital expenditures	2,007	461	5,673	1,008
Polyethylene | Olefins
Segment Reporting Information [Line Items]
Net external sales	450,482	475,503	859,914	962,647
Ethylene, Styrene And Other | Olefins
Segment Reporting Information [Line Items]
Net external sales	170,396	223,550	344,041	459,204
PVC, Caustic Soda And Other | Vinyls
Segment Reporting Information [Line Items]
Net external sales	429,878	168,762	846,866	359,289
Building Products | Vinyls
Segment Reporting Information [Line Items]
Net external sales	134,246	130,761	237,712	245,112
Intersegment sales
Segment Reporting Information [Line Items]
Net external sales	27,028	35,113	50,860	92,309
Intersegment sales | Olefins
Segment Reporting Information [Line Items]
Net external sales	26,641	34,782	50,103	91,635
Intersegment sales | Vinyls
Segment Reporting Information [Line Items]
Net external sales	$ 387	$ 331	$ 757	$ 674