Long-Term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 07, 2016	Sep. 06, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Deferred charges and other assets, net	$ 310,456			$ 176,625
Principal Amount	3,677,889			764,889
Unamortized Discount and Debt Issuance Costs,	2,696			(6,741)
Long-term debt, net	3,680,585			758,148
Unamortized debt issuance costs	21,286			5,967
Previously reported [Member]
Debt Instrument [Line Items]
Deferred charges and other assets, net				173,384
Long-term debt, net				764,115
Line of Credit [Member] | Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal Amount				0
Unamortized Discount and Debt Issuance Costs,	0			0
Long-term debt, net	325,000			0
Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount	10,889			10,889
Unamortized Discount and Debt Issuance Costs,	0			0
Long-term debt, net	10,889			10,889
Senior Notes [Member] | 4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member]
Debt Instrument [Line Items]
Principal Amount	624,793			0
Unamortized Discount and Debt Issuance Costs,	28,463			0
Long-term debt, net	$ 653,256			0
Maturity date	2021
Stated interest rate (percent)	4.625%
Senior Notes [Member] | 4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member]
Debt Instrument [Line Items]
Principal Amount	$ 63,207	$ 624,793	$ 688,000	0
Unamortized Discount and Debt Issuance Costs,	3,036			0
Long-term debt, net	$ 66,243			0
Maturity date	2021
Stated interest rate (percent)	4.625%		4.625%
Senior Notes [Member] | 3.60% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Principal Amount	$ 250,000			250,000
Unamortized Discount and Debt Issuance Costs,	(1,976)			(2,232)
Long-term debt, net	$ 248,024			247,768
Maturity date	2022
Stated interest rate (percent)	3.60%
Senior Notes [Member] | 4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member]
Debt Instrument [Line Items]
Principal Amount	$ 433,793			0
Unamortized Discount and Debt Issuance Costs,	13,958			0
Long-term debt, net	$ 447,751			0
Maturity date	2023
Stated interest rate (percent)	4.875%	4.875%
Senior Notes [Member] | 4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member]
Debt Instrument [Line Items]
Principal Amount	$ 16,207	$ 433,793	$ 450,000	0
Unamortized Discount and Debt Issuance Costs,	562			0
Long-term debt, net	$ 16,769			0
Maturity date	2023
Stated interest rate (percent)	4.875%
Senior Notes [Member] | 3.6% Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Principal Amount	$ 750,000			0
Unamortized Discount and Debt Issuance Costs,	(10,918)			0
Long-term debt, net	$ 739,082			0
Maturity date	2026
Stated interest rate (percent)	3.60%
Senior Notes [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member]
Debt Instrument [Line Items]
Maturity date	2027
Senior Notes [Member] | 6 1/2% Senior Notes Due 2029 [Member]
Debt Instrument [Line Items]
Principal Amount	$ 100,000			100,000
Unamortized Discount and Debt Issuance Costs,	(934)			(989)
Long-term debt, net	$ 99,066			99,011
Maturity date	2029
Stated interest rate (percent)	6.50%
Senior Notes [Member] | 6 3/4% Senior Notes Due 2032 [Member]
Debt Instrument [Line Items]
Principal Amount	$ 250,000			250,000
Unamortized Discount and Debt Issuance Costs,	(1,913)			(2,002)
Long-term debt, net	$ 248,087			247,998
Maturity date	2032
Stated interest rate (percent)	6.75%
Senior Notes [Member] | 2035 GO Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Principal Amount	$ 89,000			89,000
Unamortized Discount and Debt Issuance Costs,	(851)			(884)
Long-term debt, net	$ 88,149			88,116
Maturity date	2035
Stated interest rate (percent)	6.50%
Senior Notes [Member] | 2035 IKE Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Principal Amount	$ 65,000			65,000
Unamortized Discount and Debt Issuance Costs,	(610)			(634)
Long-term debt, net	$ 64,390			64,366
Maturity date	2035
Stated interest rate (percent)	6.50%
Senior Notes [Member] | 5% Senior Notes Due 2046 [Member]
Debt Instrument [Line Items]
Principal Amount	$ 700,000			0
Unamortized Discount and Debt Issuance Costs,	(26,121)			0
Long-term debt, net	$ 673,879			$ 0
Maturity date	2046
Stated interest rate (percent)	5.00%