Fair Value Of Financial Instruments (Summary Of Carrying Amount And Fair Value Of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Mortgages payable and notes payable | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	$ 750,268	$ 823,045
Mortgages payable and notes payable | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	760,260	833,931
Senior notes and debentures | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	1,976,594	1,732,551
Senior notes and debentures | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Fair value of long-term debt	$ 2,015,973	$ 1,786,758