Schedule III - Real Estate And Accumulated Depreciation (Changes In Real Estate And Accumulated Depreciation) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Real estate balance, beginning of the year		$ 1,550,027,000		$ 1,476,173,000	$ 1,450,951,000
Properties transferred to held for sale		(96,596,000)		(4,599,000)	(81,223,000)
Properties acquired		39,456,000		65,313,000	91,241,000
Impairments					(6,000)
Improvements and betterments		15,672,000		13,140,000	15,210,000
Write-off fully-depreciated assets		(12,130,000)
Real estate balance, end of the year		1,496,429,000	[1]	1,550,027,000	1,476,173,000
Accumulated depreciation balance, beginning of the year		300,832,000		267,211,000	251,605,000
Properties transferred held for sale		(11,280,000)		(1,380,000)	(18,523,000)
Depreciation expense	[2]	35,648,000		35,001,000	34,129,000
Write-off fully-depreciated assets		(12,130,000)
Accumulated depreciation balance end of the year		313,070,000		300,832,000	267,211,000
Net book value		1,183,359,000		$ 1,249,195,000	$ 1,208,962,000
Difference between recorded cost of real estate and cost for federal tax purposes		$ 26,500,000
Minimum [Member]
Estimated useful life of buildings and improvements		3 years
Maximum [Member]
Estimated useful life of buildings and improvements		40 years

[1] At December 31, 2016, the aggregate cost for federal income tax purposes was approximately $26.5 million greater than the Company's recorded values.

[2] Depreciation is provided over the estimated useful lives of the buildings and improvements, which range from 3 to 40 years.