Accounts Receivable Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts Receivable [Line Items]
Allowance for Doubtful Accounts	$ (158)	$ (102)
Receivables - customers, net	23,309	23,867
Billed Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	15,548	14,965
Unbilled Revenues [Member]
Accounts Receivable [Line Items]
Accounts Receivable, Trade	$ 7,919	$ 9,004