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Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Table) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Investment Maturity Date Range One Year Or Less [Member]
   
Investment [Line Items]    
Financial Instruments, Owned, Corporate Debt, at Fair Value $ 8,285 $ 5,659
Certificates of Deposit, at Carrying Value 8,000 0
Marketable Securities 16,285 5,659
Investment Maturity Date Range One To Eight Years [Member]
   
Investment [Line Items]    
Financial Instruments, Owned, Corporate Debt, at Fair Value 73,027 63,965
Certificates of Deposit, at Carrying Value 8,175 8,039
Marketable Securities $ 81,202 $ 72,004