v3.8.0.1
Financial Highlights (Results Of Operations For A Share Outstanding) (Details) - $ / shares
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Jun. 30, 2017
Dec. 31, 2016
Jun. 30, 2016
Dec. 31, 2015
Increase (Decrease) Equity Per Share [Roll Forward]                
Beginning Shareholders' Equity Per Share (6/30/2017, 6/30/2016, 12/31/2016, and 12/31/2015, respectively) $ 19.49 $ 20.58 $ 19.75 $ 22.10        
Net Investment Income 0.25 0.20 0.87 0.81        
Net Realized/Unrealized Gains (Losses) (0.05) (0.18) 0.00 (1.35)        
Results of Operations Attributable to Equity 0.20 0.02 0.87 (0.54)        
Less: Results of Operations Attributable to Non-controlling Interests (0.01) 0.00 (0.04) 0.00        
Results of Operations Attributable to Shareholders' Equity [1] 0.19 0.02 0.83 (0.54)        
Dividends Paid to Common Shareholders (0.45) (0.50) (1.35) (1.50)        
Weighted Average Share Impact on Dividends Paid [2] (0.01) (0.01) (0.03) (0.03)        
Accretive (Dilutive) Effect of Share Issuances (Net of Offering Costs), Share Repurchases, and Adjustments to Non-controlling Interest 0.02 0.02 0.04 0.08        
Ending Shareholders' Equity Per Share (9/30/2017, 9/30/2016, 9/30/2017, and 9/30/2016, respectively) [3] $ 19.24 $ 20.11 $ 19.24 $ 20.11        
Shares Outstanding, end of period 31,992,177 32,619,060 31,992,177 32,619,060 32,112,697 32,294,703 32,743,356 33,126,012
Shareholders Equity Per Share Upon Conversion Of All Convertible Units (in usd per share) $ 18.96 $ 19.83 $ 18.96 $ 19.83        
[1] Calculated based on average common shares outstanding and can differ from the calculation for EPS (See Note 11).
[2] Per share impact on dividends paid relating to share issuances/repurchases during the period as well as dividends paid to LTIP and OP Unit holders.
[3] If all LTIP Units and OP Units previously issued were vested and exchanged for common shares as of September 30, 2017 and 2016, shareholders' equity per share would be $18.96 and $19.83, respectively.