Deferred Charges, Goodwill And Other Assets, Net (Schedule Of Cash Flow Hedging, Derivative Financial Instruments On The Income Statement) (Details) - USD ($)
 1 Months Ended 12 Months Ended
Dec. 31, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]        
Total Amount of Interest Expense presented in the consolidated statements   $ (80,991,000) $ (90,569,000) $ (77,594,000)
Not Designated as Hedging Instrument [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income   16,000 3,551,000 2,944,000
Not Designated as Hedging Instrument [Member] | Interest And Other Investment Income (Loss) [Member] | Cash Flow Hedging [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Amount of Gain or (Loss) Recognized in Income on Derivative and Reclassification for Forecasted Transactions No Longer Probable of Occurring     1,926,000 (204,000)
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Cash Flow Hedging [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Amount of Gain or (Loss) Recognized in OCI on Derivative     (4,682,000) 5,262,000
Total Amount of Interest Expense presented in the consolidated statements   $ (80,991,000) (90,569,000) $ (77,594,000)
Designated as Hedging Instrument [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Amount of Gain or (Loss) Recognized in Income on Derivative and Reclassification for Forecasted Transactions No Longer Probable of Occurring     $ 1,900,000  
Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Amount of Gain or (Loss) Recognized in Income on Derivative and Reclassification for Forecasted Transactions No Longer Probable of Occurring $ 25,000