Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Noncontrolling Interest in OpCo	Westlake General Partner	Common units Publicly and Privately Held Limited Partner	Common units Westlake Limited Partner
Total equity at Dec. 31, 2022	$ 903,708	$ 611,778	$ (242,572)	$ 480,643	$ 53,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	91,452	76,560	0	8,921	5,971
Distribution to unitholders	(16,604)	0	0	(9,947)	(6,657)
Distribution to noncontrolling interest retained in OpCo by Westlake	(88,678)	(88,678)	0	0	0
Total equity at Mar. 31, 2023	889,878	599,660	(242,572)	479,617	53,173
Total equity at Dec. 31, 2022	903,708	611,778	(242,572)	480,643	53,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	247,569
Total equity at Sep. 30, 2023	861,272	579,030	(242,572)	474,895	49,919
Total equity at Mar. 31, 2023	889,878	599,660	(242,572)	479,617	53,173
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	75,264	63,378	0	7,120	4,766
Distribution to unitholders	(16,603)	0	0	(9,946)	(6,657)
Distribution to noncontrolling interest retained in OpCo by Westlake	(80,581)	(80,581)	0	0	0
Total equity at Jun. 30, 2023	867,958	582,457	(242,572)	476,791	51,282
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	80,853	67,647	0	7,911	5,295
Units issued for vested phantom units	141	0	0	141	0
Distribution to unitholders	(16,606)	0	0	(9,948)	(6,658)
Distribution to noncontrolling interest retained in OpCo by Westlake	(71,074)	(71,074)	0	0	0
Total equity at Sep. 30, 2023	861,272	579,030	(242,572)	474,895	49,919
Total equity at Dec. 31, 2023	856,250	576,316	(242,572)	473,513	48,993
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	89,646	74,813	0	8,887	5,946
Distribution to unitholders	(16,607)	0	0	(9,950)	(6,657)
Distribution to noncontrolling interest retained in OpCo by Westlake	(81,044)	(81,044)	0	0	0
Total equity at Mar. 31, 2024	848,245	570,085	(242,572)	472,450	48,282
Total equity at Dec. 31, 2023	856,250	576,316	(242,572)	473,513	48,993
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	281,772
Total equity at Sep. 30, 2024	837,814	560,070	(242,572)	472,296	48,020
Total equity at Mar. 31, 2024	848,245	570,085	(242,572)	472,450	48,282
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	88,026	73,599	0	8,644	5,783
Units issued for vested phantom units	55	0	0	55	0
Distribution to unitholders	(16,607)	0	0	(9,950)	(6,657)
Distribution to noncontrolling interest retained in OpCo by Westlake	(84,872)	(84,872)	0	0	0
Total equity at Jun. 30, 2024	834,847	558,812	(242,572)	471,199	47,408
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	104,100	85,964	0	10,867	7,269
Units issued for vested phantom units	183	0	0	183	0
Distribution to unitholders	(16,610)	0	0	(9,953)	(6,657)
Distribution to noncontrolling interest retained in OpCo by Westlake	(84,706)	(84,706)	0	0	0
Total equity at Sep. 30, 2024	$ 837,814	$ 560,070	$ (242,572)	$ 472,296	$ 48,020