Concentrations of Credit Risk and Major Customers (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Customer	Dec. 31, 2011 Customer	Dec. 31, 2010 Customer
Concentration Risk
Concentration of risk, number of customers	5
Sales Revenue, Services, Net [Member] | Customer Concentration Risk [Member]
Concentration Risk
Concentration of risk, number of customers	1	1	1
Concentration Risk, Percentage	39.00%	38.00%	38.00%
Entity-Wide Revenue, Major Customer, Amount	$ 60.4	$ 69.3	$ 62.9
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration Risk
Concentration Risk, Percentage	31.00%	32.00%