Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest in OpCo [Member]	Westlake [Member] General Partner [Member]	Common units [Member] Public [Member] Limited Partner [Member]	Common units [Member] Westlake [Member] Limited Partner [Member]	Subordinated units [Member] Westlake [Member] Limited Partner [Member]
Equity, beginning balance at Dec. 31, 2014	$ 834,950	$ 0	$ 747,426	$ (242,572)	$ 290,377	$ 4,038	$ 35,681
Net income	262,678		233,632		13,887	1,542	13,617
Net effect of cash flow hedge	(173)	(173)
Quarterly distributions to unitholders	(22,972)				(10,982)	(1,220)	(10,770)
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(238,009)		(238,009)
Equity, ending balance at Sep. 30, 2015	836,474	(173)	743,049	(242,572)	293,282	4,360	38,528
Equity, beginning balance at Dec. 31, 2015	847,167	280	750,606	(242,572)	294,565	4,502	39,786
Net income	259,822		229,733	139	14,320	1,589	14,041
Net effect of cash flow hedge	(504)	(504)
Quarterly distributions to unitholders	(25,774)		0	(48)	(12,300)	(1,365)	(12,061)
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(188,736)		(188,736)
Equity, ending balance at Sep. 30, 2016	$ 891,975	$ (224)	$ 791,603	$ (242,481)	$ 296,585	$ 4,726	$ 41,766