Quarterly Financial Information (Unaudited) (Summary Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales	$ 308,645	$ 296,775	$ 290,113	$ 277,448	$ 293,937	$ 229,354	$ 210,841	$ 252,604	$ 1,172,981	$ 986,736	$ 1,007,221
Gross profit	110,732	95,403	99,571	97,961	105,735	86,801	88,381	110,414	403,667	391,331	382,882
Income from operations	102,991	88,598	92,685	90,133	98,581	81,013	82,533	104,317	374,407	366,444	359,332
Net income	98,315	82,245	86,470	86,028	93,581	75,859	81,192	102,771	353,058	353,403	353,853
Net income attributable to Westlake Chemical Partners LP	$ 15,546	$ 13,385	$ 9,975	$ 9,764	$ 10,851	$ 8,661	$ 9,344	$ 12,084	$ 48,670	$ 40,940	$ 39,831
Weighted Average Number of Shares Outstanding, Basic and Diluted									28,392,470	27,059,730	27,059,730
Common units [Member]
Net income attributable to Westlake Chemical Partners LP									$ 38,010	$ 21,597	$ 21,158
Basic and diluted earnings per common unit holder (usd per unit)	$ 0.46	$ 0.47	$ 0.36	$ 0.35	$ 0.39	$ 0.32	$ 0.34	$ 0.45	$ 1.72	$ 1.50	$ 1.47
Weighted Average Number of Shares Outstanding, Basic and Diluted	32,234,730	32,234,730	14,373,615	14,373,615	14,373,615	14,373,615	14,373,615	14,373,615	22,101,547	14,373,615	14,373,615
Subordinated units [Member]
Net income attributable to Westlake Chemical Partners LP									$ 8,994	$ 19,062	$ 18,673
Basic and diluted earnings per common unit holder (usd per unit)	$ 0.00	$ 0.00	$ 0.36	$ 0.35	$ 0.39	$ 0.32	$ 0.34	$ 0.45	$ 1.43	$ 1.50	$ 1.47
Weighted Average Number of Shares Outstanding, Basic and Diluted	0	0	12,686,115	12,686,115	12,686,115	12,686,115	12,686,115	12,686,115	6,290,923	12,686,115	12,686,115