Financial Highlights (Results Of Operations For A Share Outstanding) (Details) - $ / shares		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) Equity Per Share [Roll Forward]
Beginning Shareholders' Equity Per Share (12/31/2016 and 12/31/2015, respectively)		$ 19.75	$ 22.10
Net Investment Income		0.37	0.36
Net Realized/Unrealized Gains (Losses)		0.11	(1.06)
Results of Operations Attributable to Equity		0.48	(0.70)
Less: Results of Operations Attributable to Non-controlling Interests		(0.01)	0.00
Results of Operations Attributable to Shareholders' Equity	[1]	0.47	(0.70)
Dividends Paid to Common Shareholders		(0.45)	(0.50)
Weighted Average Share Impact on Dividends Paid	[2]	(0.01)	(0.01)
Accretive (Dilutive) Effect of Share Issuances (Net of Offering Costs), Share Repurchases, and Adjustments to Non-controlling Interest		0.02	0.02
Ending Shareholders' Equity Per Share (3/31/2017 and 3/31/2016, respectively)(3)	[3]	$ 19.78	$ 20.91
Shares Outstanding, end of period		32,164,215	32,962,979	32,294,703	33,126,012
Shareholders Equity Per Share Upon Conversion Of All Convertible Units (in usd per share)		$ 19.50	$ 20.63

[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 March 31, 2017 and 2016, shareholders' equity per share would be $19.50 and $20.63, respectively.