Receivables (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	$ 250,868	$ 216,732
Allowance for doubtful accounts receivable	(796)	(125)
Net receivables	250,072	216,607
Accounts receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	248,462	214,608
Notes receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	99	16
Other receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross receivables	$ 2,307	$ 2,108