Receivables (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	$ 22,520	$ 21,834
Receivables, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Income taxes receivable	16,500	29,000
Nontrade receivables	10,500	10,400
Escrow | Receivables, net | Environmental services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	$ 8,000	$ 8,000