Accounts Receivable Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 437,083	$ 430,210
Allowance for doubtful accounts	(14,356)	(13,505)
Accounts receivable, net	422,727	416,705
Accounts receivable - trade [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	400,926	401,723
Accounts receivable - grants from outside parties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	16,142	17,734	$ 7,900
Accounts receivable - insurance and other third-party claims [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 20,015	$ 10,753