Earnings Per Share (Anti-Dilutive Securities) (Details) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	3,941		5,664		3,942		5,412
Share Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	2,359	[1]	3,163	[1]	2,359	[1]	2,846	[1]
Operating Partnership Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	1,582		1,607		1,583		1,626
Share Options And Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive securities	0		894		0		940

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