Schedule III - Real Estate and Accumulated Depreciation (Changes in Real Estate and Accumulated Depreciation) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Real estate balance, beginning of the year		$ 1,508,682,000		$ 1,534,599,000	$ 1,496,429,000
Properties transferred to held for sale		(36,265,000)		(61,505,000)	(15,971,000)
Property acquisitions		9,333,000		6,481,000	30,997,000
Property dispositions					(4,332,000)
Improvements and betterments		37,089,000		29,107,000	29,752,000
Asset write-offs		(3,633,000)			(2,276,000)
Real estate balance, end of the year		1,515,206,000	[1]	1,508,682,000	1,534,599,000
Accumulated depreciation balance, beginning of the year		361,969,000		341,943,000	313,070,000
Properties transferred to held for sale		(10,143,000)		(14,886,000)	(4,131,000)
Property dispositions					(1,048,000)
Depreciation expense	[2]	41,142,000		34,912,000	36,328,000
Asset write-offs		(3,107,000)			(2,276,000)
Accumulated depreciation balance end of the year		389,861,000		361,969,000	341,943,000
Net book value		1,125,345,000		$ 1,146,713,000	$ 1,192,656,000
Amount of encumbrance		46,700,000
Difference between recorded cost of real estate and cost for federal tax purposes		$ 5,700,000
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, 2019, the aggregate cost for federal income tax purposes was approximately $5.7 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.