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Line Of Credit (Details) - Line of Credit [Member] - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Line of Credit Facility [Line Items]      
Debt Instrument, Term 5 years    
Credit facility $ 300,000    
Credit facility, expiration date Feb. 02, 2017    
Credit facility, commitment fee per annum on daily unused portion, percent 0.15%    
Aggregate amount that may increase under credit facility $ 100,000    
Credit Facility, commitment fees $ 483 $ 458 $ 458
London Interbank Offered Rate (LIBOR) [Member]      
Line of Credit Facility [Line Items]      
Credit facility interest accrued, percentage above LIBOR 1.25%