Concentrations of Credit Risk and Major Customers (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 Customer	Dec. 31, 2012	Dec. 31, 2011
Concentration Risk
Concentration of risk, number of customers									5
Entity-Wide Revenue, Major Customer, Amount	$ 183,348	$ 130,645	$ 133,992	$ 134,273	$ 136,192	$ 135,010	$ 139,710	$ 134,833	$ 582,257	$ 545,745	$ 528,623
Sales Revenue, Services, Net [Member] | Customer Concentration Risk [Member]
Concentration Risk
Concentration of risk, number of customers									0	1	1
Baseline percentage for customer concentration of risk									10.00%	10.00%	10.00%
Concentration Risk, Percentage									32.00%	39.00%	38.00%
Entity-Wide Revenue, Major Customer, Amount										$ 60,400	$ 69,300
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration Risk
Concentration Risk, Percentage									20.00%	31.00%