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, 2015	$ 847,167	$ 280	$ 750,606	$ (242,572)	$ 294,565	$ 4,502	$ 39,786
Net income	183,963	0	162,535	48	10,222	1,135	10,023
Net effect of cash flow hedge	(904)	(904)	0	0	0	0	0
Quarterly distributions to unitholders	(16,910)	0	0	(2)	(8,083)	(898)	(7,927)
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(149,566)	0	(149,566)	0	0	0	0
Equity, ending balance at Jun. 30, 2016	863,750	(624)	763,575	(242,526)	296,704	4,739	41,882
Equity, beginning balance at Dec. 31, 2016	920,963	200	818,479	(242,430)	297,367	4,813	42,534
Net income	172,498	0	152,759	554	9,174	1,017	8,994
Net effect of cash flow hedge	43	43	0	0	0	0	0
Quarterly distributions to unitholders	(19,313)	0	0	(374)	(9,055)	(1,005)	(8,879)
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(178,388)	0	(178,388)	0	0	0	0
Equity, ending balance at Jun. 30, 2017	$ 895,803	$ 243	$ 792,850	$ (242,250)	$ 297,486	$ 4,825	$ 42,649