Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Net external sales	$ 1,188,037	$ 1,253,227	$ 3,476,570	$ 3,279,479
Income (loss) from operations	254,028	306,761	778,682	821,604
Depreciation and amortization	61,248	53,920	180,229	148,394
Other income (expense), net	2,636	(2,670)	33,790	4,440
Provision for (benefit from) income taxes	60,033	124,449	236,824	300,231
Capital expenditures	125,304	94,271	329,236	311,183
Olefins
Segment Reporting Information [Line Items]
Net external sales	588,097	703,097	1,792,052	2,124,948
Income (loss) from operations	196,703	259,277	608,744	770,267
Depreciation and amortization	27,678	26,443	82,240	79,811
Other income (expense), net	1,323	1,609	3,770	4,262
Provision for (benefit from) income taxes	45,865	105,030	186,534	282,082
Capital expenditures	69,885	48,519	206,719	121,041
Vinyls
Segment Reporting Information [Line Items]
Net external sales	599,940	550,130	1,684,518	1,154,531
Income (loss) from operations	67,779	59,445	202,831	76,460
Depreciation and amortization	33,432	27,336	97,615	68,127
Other income (expense), net	10	1,189	6,927	942
Provision for (benefit from) income taxes	15,812	21,761	55,270	22,121
Capital expenditures	53,510	44,067	114,935	187,449
Corporate and Other
Segment Reporting Information [Line Items]
Income (loss) from operations	(10,454)	(11,961)	(32,893)	(25,123)
Depreciation and amortization	138	141	374	456
Other income (expense), net	1,303	(5,468)	23,093	(764)
Provision for (benefit from) income taxes	(1,644)	(2,342)	(4,980)	(3,972)
Capital expenditures	1,909	1,685	7,582	2,693
Polyethylene | Olefins
Segment Reporting Information [Line Items]
Net external sales	423,631	498,450	1,283,545	1,461,097
Ethylene, Styrene And Other | Olefins
Segment Reporting Information [Line Items]
Net external sales	164,466	204,647	508,507	663,851
PVC, Caustic Soda And Other | Vinyls
Segment Reporting Information [Line Items]
Net external sales	468,235	416,771	1,315,101	776,060
Building Products | Vinyls
Segment Reporting Information [Line Items]
Net external sales	131,705	133,359	369,417	378,471
Intersegment sales
Segment Reporting Information [Line Items]
Net external sales	28,892	26,873	79,752	119,182
Intersegment sales | Olefins
Segment Reporting Information [Line Items]
Net external sales	28,551	26,518	78,654	118,153
Intersegment sales | Vinyls
Segment Reporting Information [Line Items]
Net external sales	$ 341	$ 355	$ 1,098	$ 1,029