Receivables (Details) (USD $)									3 Months Ended	9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 Accounts Receivable [Member]	Dec. 31, 2010 Accounts Receivable [Member]	Sep. 30, 2011 Notes Receivable [Member]	Dec. 31, 2010 Notes Receivable [Member]	Sep. 30, 2011 Other Receivables [Member]	Dec. 31, 2010 Other Receivables [Member]	Sep. 30, 2010 Allowance for Doubtful Accounts, Current [Member]	Sep. 30, 2011 Allowance for Doubtful Accounts, Current [Member]	Sep. 30, 2010 Allowance for Doubtful Accounts, Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	$ 163,099,000	$ 127,558,000	$ 162,546,000	$ 126,671,000	$ 80,000	$ 139,000	$ 473,000	$ 748,000
Allowance for doubtful accounts receivable	(313,000)	(260,000)
Net receivables	162,786,000	127,298,000
Valuation and Qualifying Accounts Disclosure [Line Items]
Bad debt expense									100,000	100,000
Collections on previous bad debts											$ 100,000