Accounts Receivable Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 445,230	$ 430,210
Allowance for doubtful accounts	(9,081)	(13,505)
Accounts receivable, net	436,149	416,705
Accounts receivable - trade [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	423,050	401,723
Accounts receivable - grants from outside parties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	10,885	17,734	$ 10,000
Accounts receivable - insurance and other third-party claims [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 11,295	$ 10,753