Common Share Capitalization (Summary Of Common Shares Outstanding) (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Shares Outstanding, period begin	32,294,703	33,126,012	33,449,678
Shares repurchased	(961,566)	(833,784)	(325,613)
Director LTIP Units exercised	2,801	2,475	1,947
Common Shares Outstanding, period end	31,335,938	32,294,703	33,126,012