Quarterly Financial Information (Unaudited) (Summary Of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues	$ 272,798	$ 249,925	$ 270,062	$ 299,086	$ 335,725	$ 363,650	$ 301,975	$ 284,272	$ 1,091,871	$ 1,285,622	$ 1,172,981
Gross profit	103,597	93,219	91,958	90,654	93,629	93,907	97,118	92,505	379,428	377,159	403,667
Income from operations	95,753	86,397	84,319	83,681	86,456	87,998	89,743	85,372	350,150	349,569	374,407
Net income	91,910	82,479	80,110	78,396	81,582	83,799	84,476	80,714	332,895	330,571	353,058
Net income attributable to Westlake Chemical Partners LP	$ 17,371	$ 14,922	$ 13,733	$ 14,955	$ 11,883	$ 12,412	$ 12,757	$ 12,295	$ 60,981	$ 49,347	$ 48,670
Weighted Average Number of Shares Outstanding, Basic and Diluted									34,488,058	32,240,858	28,392,470
Common units [Member]
Net income attributable to Westlake Chemical Partners LP									$ 60,981	$ 48,614	$ 38,010
Basic and diluted earnings per common unitholder	$ 0.49	$ 0.42	$ 0.39	$ 0.46	$ 0.37	$ 0.38	$ 0.40	$ 0.36
Weighted Average Number of Shares Outstanding, Basic and Diluted	35,191,487	35,188,189	35,188,189	32,345,398	32,247,371	32,242,210	32,237,266	32,237,266	34,488,058	32,240,858	22,101,547