Financial Highlights (Net Asset Based Total Return For A Shareholder Assuming Conversion Of All LTIP Units) (Details)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2012 Long-Term Incentive Plan Units [Member]	Dec. 31, 2011 Long-Term Incentive Plan Units [Member]	Dec. 31, 2010 Long-Term Incentive Plan Units [Member]	Dec. 31, 2009 Long-Term Incentive Plan Units [Member]
Financial Highlights [Line Items]
Total Return	19.82%	[1]
LTIP units outstanding			397,096	390,500	385,000	382,500
Percentage of LTIP units outstanding			1.91%

[1] Total return is calculated assuming all LTIP units had been converted into common shares at December 31, 2012. Total return represents all shareholders’ equity accounts outstanding for the entire period. LTIP units outstanding at December 31, 2012 totaled 397,096 and represent 1.91% of total shares and LTIP units outstanding as of that date.