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Rental Properties Summary Of Carrying Amounts Of Rental Properties (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Real Estate Properties [Line Items]      
Real Estate Investment Property Gross $ 2,513,794,000 $ 2,260,777,000  
Accumulated depreciation (409,643,000) (375,684,000)  
Total 2,104,151,000 1,885,093,000  
Depreciation expense on rental properties 50,700,000 43,800,000 40,000,000
Building and Building Improvements [Member]
     
Real Estate Properties [Line Items]      
Real Estate Investment Property Gross 1,937,661,000 1,734,300,000  
Furniture and Fixtures [Member]
     
Real Estate Properties [Line Items]      
Real Estate Investment Property Gross 26,676,000 34,028,000  
Land [Member]
     
Real Estate Properties [Line Items]      
Real Estate Investment Property Gross $ 549,457,000 $ 492,449,000