Earnings Per Share (Anti-Dilutive Securities) (Details) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	3,944		4,991		3,945		4,020
Share Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	2,362	[1]	2,383	[1]	2,362	[1]	2,384	[1]
Operating Partnership Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	1,582		1,628		1,583		1,636
Share Options And Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	0		980		0		0

[1] Exclusion results as exercise prices were greater than the average market price for each respective period.