Receivables (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	$ 216,732,000	$ 127,558,000
Allowance for doubtful accounts receivable	(125,000)	(260,000)
Net receivables	216,607,000	127,298,000
Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	214,608,000	126,671,000
Notes Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	16,000	139,000
Other Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	2,108,000	748,000
Allowance for Doubtful Accounts, Current [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Collections on previous bad debts	$ 100,000	$ 100,000	$ 1,800,000