Financial Highlights (Results Of Operations For A Share Outstanding) (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Increase (Decrease) Earnings Per Share [Roll Forward]
Beginning Shareholders' Equity Per Share (6/30/2013, 6/30/2012, 12/31/2012, and 12/31/2011, respectively)	$ 24.92		$ 24.03		$ 24.86		$ 22.55
Net Investment Income	$ 0.57		$ 0.04		$ 1.62		$ 1.21
Net Realized/Unrealized Gains (Losses)	$ (0.10)		$ 1.59		$ 1.18		$ 3.04
Results of Operations Attributable to Equity	$ 0.47		$ 1.63		$ 2.80		$ 4.25
NetIncomeLossAttributableToNoncontrollingInterestPerShare	$ 0.00		$ 0.00		$ (0.03)		$ 0.00
NetIncomeLossAttributableToParentPerShare	$ 0.47	[1]	$ 1.63	[1]	$ 2.77	[1]	$ 4.25	[1]
Dividends Paid Per Common Share	$ (0.77)		$ (0.70)		$ (3.06)		$ (1.80)
Weighted Average Share Impact on Dividends Paid (2)	$ (0.02)	[2]	$ (0.08)	[2]	$ (0.08)	[2]	$ (0.12)	[2]
Accretive (Dilutive) Effect of Share Issuances (Net of Offering Costs) and Share Repurchases	$ (0.01)		$ (0.54)		$ 0.10		$ (0.54)
Ending Shareholders' Equity Per Share (9/30/2013, 9/30/2012, 9/30/2013, and 9/30/2012, respectively)(3)	$ 24.59	[3]	$ 24.34	[3]	$ 24.59	[3]	$ 24.34	[3]
Shares Outstanding, end of period	25,418,937		20,483,696		25,418,937		20,483,696		25,412,011	20,370,469	16,447,651	16,447,651
Shareholders Equity Per Share Upon Conversion Of All Convertible Units (in usd per share)	$ 24.19				$ 24.19
Shareholders' equity per share upon conversion of LTIPs (in usd per share)			$ 23.88				$ 23.88			$ 24.38

[1] Calculated based on average common shares outstanding and can differ from the calculation for EPS (See Note 9).

[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 (if applicable) previously issued were vested and exchanged for common shares as of September 30, 2013 and 2012, shareholders' equity per share would be $24.19 and $23.88, respectively.