Schedule III - Real Estate and Accumulated Depreciation (Changes in Real Estate and Accumulated Depreciation) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Real estate balance, beginning of the year		$ 1,515,206,000		$ 1,508,682,000	$ 1,534,599,000
Properties transferred to held for sale		(22,512,000)		(36,265,000)	(61,505,000)
Property acquisitions				9,333,000	6,481,000
Outparcel dispositions		(840,000)
Improvements and betterments		35,624,000		37,089,000	29,107,000
Asset write-offs				(3,633,000)
Real estate balance, end of the year		1,527,478,000	[1]	1,515,206,000	1,508,682,000
Accumulated depreciation balance, beginning of the year		389,861,000		361,969,000	341,943,000
Properties transferred to held for sale		(3,947,000)		(10,143,000)	(14,886,000)
Outparcel dispositions		(90,000)
Depreciation expense	[2]	42,745,000		41,142,000	34,912,000
Asset write-offs				(3,107,000)
Accumulated depreciation balance end of the year		428,569,000		389,861,000	361,969,000
Net book value		1,098,909,000		$ 1,125,345,000	$ 1,146,713,000
Amount of encumbrance		45,600,000
Difference between recorded cost of real estate and cost for federal tax purposes		$ 25,600,000
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, 2020, the aggregate cost for federal income tax purposes was approximately $25.6 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.