Related Party Transactions (General) (Details) - Affiliated Entity [Member] - Westlake [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Operating Lease, Expense	$ 514	$ 318
Interest earned related to the IMA	818	$ 540
Accrued Liabilities [Member]
Related Party Transaction [Line Items]
Accrued interest included in receivable under IMA	$ 34		$ 496