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Other Assets and Deferred Charges, Net (Narrative) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Deferred Costs And Other Assets [Line Items]      
Amortization expense of deferred charges $ 5.3 $ 5.2 $ 5.1
Unsecured Revolving Credit Facility [Member]      
Deferred Costs And Other Assets [Line Items]      
Accumulated amortization of deferred lease origination costs 32.8    
Accumulated amortization of deferred financing costs $ 1.4