Financial Highlights (Results Of Operations For A Share Outstanding) (Details) - $ / shares		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Increase (Decrease) Equity Per Share [Roll Forward]
Beginning Shareholders' Equity Per Share (12/31/2016, 12/31/2015, and 12/31/2014, respectively)		$ 19.75	[1]	$ 22.10	[1]	$ 23.38
Net Investment Income		1.10		1.09		1.98
Net Realized/Unrealized Gains (Losses)		0.02		(1.57)		(0.83)
Results of Operations Attributable to Equity		1.12		(0.48)		1.15
Less: Results of Operations Attributable to Non-controlling Interests		(0.06)		(0.01)		(0.01)
Results of Operations Attributable to Shareholders' Equity	[2]	1.06		(0.49)		1.14
Dividends Paid to Common Shareholders		(1.76)		(1.95)		(2.45)
Weighted Average Share Impact on Dividends Paid	[3]	(0.04)		(0.04)		(0.05)
Accretive (Dilutive) Effect of Share Issuances (Net of Offering Costs), Share Repurchases, and Adjustments to Non-controlling Interest		0.14		0.13		0.08
Ending Shareholders' Equity Per Share (12/31/2017, 12/31/2016 and 12/31/2015, respectively)	[1]	$ 19.15		$ 19.75		$ 22.10
Shares Outstanding, end of period		31,335,938		32,294,703		33,126,012	33,449,678
Shareholders Equity Per Share Upon Conversion Of All Convertible Units (in usd per share)		$ 18.85		$ 19.46		$ 21.80

[1] If all LTIP Units and OP Units previously issued were vested and exchanged for common shares as of December 31, 2017, 2016, and 2015, shareholders' equity per share would be $18.85, $19.46, and $21.80, respectively.

[2] Calculated based on average common shares outstanding and can differ from the calculation for EPS (See Note 13).

[3] 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.