Related Party Transactions (Cost of Sales from Related Parties) (Details) - Affiliated Entity [Member] - Westlake [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	$ 134,195	$ 86,278	$ 388,127	$ 243,877
Feedstock purchased [Member]
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	110,241	63,693	313,231	181,174
Other service charges [Member]
Related Party Transaction [Line Items]
Charges from related parties in cost of sales	$ 23,954	$ 22,585	$ 74,896	$ 62,703