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Debt And Interest Expense (Credit Facilities) (Narrative) (Details)
1 Months Ended 3 Months Ended 12 Months Ended
Mar. 27, 2015
Apr. 30, 2013
Mar. 31, 2015
Dec. 31, 2016
USD ($)
Debt Instrument [Line Items]        
Borrowing capacity of senior unsecured revolving credit facility       $ 200,000,000.0
Credit facility, maturity date Apr. 01, 2025 May 01, 2023 Apr. 01, 2020  
Aggregate increase of commitment amount available       $ 150,000,000.0
Minimum [Member]        
Debt Instrument [Line Items]        
Interest coverage ratio       3.0
Maximum [Member]        
Debt Instrument [Line Items]        
Leverage ratio       2.5