Annual report pursuant to Section 13 and 15(d)

Real Estate Investments And Accumulated Depreciation (Schedule Of Changes In Rental Properties And Accumulated Depreciation) (Details)

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Real Estate Investments And Accumulated Depreciation (Schedule Of Changes In Rental Properties And Accumulated Depreciation) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Real Estate Investments And Accumulated Depreciation [Abstract]      
Rental Properties, Balance at beginning of year $ 4,958,179 $ 5,129,933 $ 5,379,436
Rental Properties, Additions 219,227 193,005 317,994
Rental Properties, Rental property held for sale     (107,205)
Rental Properties, Properties sold (82,015) (331,181) (256,335)
Rental Properties, Impairment charge (255,849)   (149,030)
Rental Properties, Retirements/disposals (31,824) (33,578) (54,927)
Rental Properties, Balance at end of year 4,807,718 4,958,179 5,129,933
Accumulated Depreciation, Balance at beginning of year 1,414,305 1,400,988 1,478,214
Accumulated Depreciation, Depreciation expense 147,447 143,278 155,846
Accumulated Depreciation, Rental property held for sale     (35,594)
Accumulated Depreciation, Properties sold (7,517) (96,383) (104,196)
Accumulated Depreciation, Impairment charge (57,929)   (38,353)
Accumulated Depreciation, Retirements/disposals (31,824) (33,578) (54,929)
Accumulated Depreciation, Balance at end of year $ 1,464,482 [1] $ 1,414,305 $ 1,400,988
[1] Depreciation of buildings and improvements are calculated over lives ranging from the life of the lease to 40 years.