Accounts Receivable Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 449,995	$ 436,360
Allowance for doubtful accounts	(10,468)	(10,055)
Accounts receivable, net	439,527	426,305
Accounts receivable - trade [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	399,157	397,255
Accounts receivable - grants from outside parties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	17,263	19,376	$ 16,100
Accounts receivable - insurance and other third-party claims [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 33,575	$ 19,729