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, 2016	$ 920,963	$ 200	$ 818,479	$ (242,430)	$ 297,367	$ 4,813	$ 42,534
Net income	86,028	0	76,264	231	4,559	505	4,469
Net effect of cash flow hedge	89	89	0	0	0	0	0
Quarterly distributions to unitholders	(9,478)	0	0	(142)	(4,464)	(495)	(4,377)
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(89,617)	0	(89,617)	0	0	0	0
Equity, ending balance at Mar. 31, 2017	907,985	289	805,126	(242,341)	297,462	4,823	42,626
Equity, beginning balance at Dec. 31, 2017	998,749	279	778,935	(241,958)	411,228	50,265	0
Net income	80,714	0	68,419	733	6,498	5,064	0
Net effect of cash flow hedge	19	19	0	0	0	0	0
Units issued for vested phantom units	60	0	0	0	60	0	0
Quarterly distributions to unitholders	(13,071)	0	0	(614)	(7,000)	(5,457)	0
Quarterly distribution to noncontrolling interest retained in OpCo by Westlake	(91,148)	0	(91,148)	0	0	0	0
Equity, ending balance at Mar. 31, 2018	$ 975,323	$ 298	$ 756,206	$ (241,839)	$ 410,786	$ 49,872	$ 0