Related Party Transactions (Details) - Unconsolidated Affiliates - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Sales to unconsolidated affiliates	$ 29,514	$ 29,651	$ 24,180
Purchases from unconsolidated affiliates(a)	209,266	130,287	$ 115,697
Receivable from related parties	2,406	2,159
Payable to related parties	$ 55,801	$ 38,466

Amount for accounts payable to related parties.

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