Related Party Transactions (Goods and Services Purchased from Westlake and Capitalized as Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Affiliated Entity [Member] \| Westlake [Member]
Related Party Transaction [Line Items]
Goods and services purchased from Westlake and capitalized as assets	$ 384	$ 641	$ 864	$ 1,284

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration