Components of Rental Income and Expense (Components Of Rental Expenses) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Component of Operating Other Cost and Expense [Line Items]
Repairs and maintenance	$ 41,977	$ 42,278	$ 40,874
Utilities	18,823	18,545	17,926
Management fees and costs	14,989	14,641	14,342
Payroll	8,080	7,909	7,770
Bad debt expense	2,649	6,396	6,488
Ground rent	2,047	3,049	4,458
Insurance	5,282	5,054	4,865
Marketing	6,868	4,789	4,843
Other operating	8,834	7,858	6,778
Rental expenses	$ 109,549	$ 110,519	$ 108,344