Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 168,575	$ 135,304
Less: allowance for doubtful accounts	(2,807)	(3,079)	(3,764)	(2,907)
Accounts receivable, net	165,768	132,225
Accounts receivable - trade [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	147,822	118,265
Accounts receivable - grants [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 20,753	$ 17,039