Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 311,837	$ 265,642
Less: Allowance for doubtful accounts	(2,523)	(2,693)
Accounts receivable, net	309,314	262,949
Accounts receivable - trade [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	262,729	212,405
Accounts receivable - grants [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	36,860	26,794
Accounts receivable - insurance claims [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 12,248	$ 26,443