Related Party Transactions (Details) - Unconsolidated Affiliates - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Sales to unconsolidated affiliates	$ 4,970	$ 7,309	$ 20,608	$ 23,753
Purchases from unconsolidated affiliates(a)	60,136	$ 51,983	186,111	$ 148,502
Receivables from unconsolidated affiliates	2,734		2,734		$ 2,406
Payables to unconsolidated affiliates	$ 54,227		$ 54,227		$ 55,801

Amount for accounts payable to related parties.

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