Schedule III - Real Estate And Accumulated Depreciation (Details)		12 Months Ended
		Dec. 31, 2018 USD ($) property		Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Gross Leasable Area | property		8,729,428
Initial cost to the Company, Land		$ 297,774,000
Initial cost to the Company, Building and Improvements		922,425,000
Subsequent cost capitalized	[1]	288,483,000
Gross carrying amount of Land		295,734,000
Gross carrying amount of building and improvements		1,212,948,000
SEC Schedule III, Real Estate, Gross, Total		1,508,682,000	[2]	$ 1,534,599,000	$ 1,496,429,000	$ 1,550,027,000
Accumulated Depreciation		$ 361,969,000		$ 341,943,000	$ 313,070,000	$ 300,832,000
Academy Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2001
Percent Owned		100.00%
Gross Leasable Area | property		137,415
Initial cost to the Company, Land		$ 2,406,000
Initial cost to the Company, Building and Improvements		9,623,000
Subsequent cost capitalized	[1]	4,900,000
Gross carrying amount of Land		2,406,000
Gross carrying amount of building and improvements		14,523,000
SEC Schedule III, Real Estate, Gross, Total		16,929,000
Accumulated Depreciation		$ 5,756,000
Academy Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1965
Academy Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2013
Big Y Shopping Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2013
Percent Owned		100.00%
Year built/Year last renovated		2007
Gross Leasable Area | property		101,105
Initial cost to the Company, Land		$ 11,272,000
Initial cost to the Company, Building and Improvements		23,395,000
Subsequent cost capitalized	[1]	260,000
Gross carrying amount of Land		10,268,000
Gross carrying amount of building and improvements		24,659,000
SEC Schedule III, Real Estate, Gross, Total		34,927,000
Accumulated Depreciation		$ 4,135,000
Camp Hill [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2002
Percent Owned		100.00%
Gross Leasable Area | property		423,671
Initial cost to the Company, Land		$ 4,460,000
Initial cost to the Company, Building and Improvements		17,857,000
Subsequent cost capitalized	[1]	39,918,000
Gross carrying amount of Land		4,093,000
Gross carrying amount of building and improvements		58,142,000
SEC Schedule III, Real Estate, Gross, Total		62,235,000
Accumulated Depreciation		$ 21,093,000
Camp Hill [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1958
Camp Hill [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2005
Carmans Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Gross Leasable Area | property		195,283
Initial cost to the Company, Land		$ 8,539,000
Initial cost to the Company, Building and Improvements		35,804,000
Subsequent cost capitalized	[1]	12,689,000
Gross carrying amount of Land		8,421,000
Gross carrying amount of building and improvements		48,611,000
SEC Schedule III, Real Estate, Gross, Total		57,032,000
Accumulated Depreciation		$ 11,730,000
Carmans Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1954
Carmans Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2007
Christina Crossing [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2017
Percent Owned		100.00%
Year built/Year last renovated		2008
Gross Leasable Area | property		119,353
Initial cost to the Company, Land		$ 4,341,000
Initial cost to the Company, Building and Improvements		23,227,000
Subsequent cost capitalized	[1]	638,000
Gross carrying amount of Land		4,341,000
Gross carrying amount of building and improvements		23,865,000
SEC Schedule III, Real Estate, Gross, Total		28,206,000
Accumulated Depreciation		$ 1,707,000
Coliseum Marketplace [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Gross Leasable Area | property		106,648
Initial cost to the Company, Land		$ 2,924,000
Initial cost to the Company, Building and Improvements		14,416,000
Subsequent cost capitalized	[1]	5,551,000
Gross carrying amount of Land		3,586,000
Gross carrying amount of building and improvements		19,305,000
SEC Schedule III, Real Estate, Gross, Total		22,891,000
Accumulated Depreciation		$ 7,396,000
Coliseum Marketplace [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1987
Coliseum Marketplace [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2012
Colonial Commons [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2011
Percent Owned		100.00%
Gross Leasable Area | property		408,642
Initial cost to the Company, Land		$ 9,367,000
Initial cost to the Company, Building and Improvements		37,496,000
Subsequent cost capitalized	[1]	5,673,000
Gross carrying amount of Land		9,367,000
Gross carrying amount of building and improvements		43,169,000
SEC Schedule III, Real Estate, Gross, Total		52,536,000
Accumulated Depreciation		$ 13,251,000
Colonial Commons [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2011
Colonial Commons [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2013
Crossroads II [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2008
Percent Owned		60.00%
Year built/Year last renovated		2009
Gross Leasable Area | property		133,717
Initial cost to the Company, Land		$ 15,383,000
Subsequent cost capitalized	[1]	29,440,000
Gross carrying amount of Land		17,671,000
Gross carrying amount of building and improvements		27,152,000
SEC Schedule III, Real Estate, Gross, Total		44,823,000
Accumulated Depreciation		$ 6,611,000
East River Park [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2015
Percent Owned		100.00%
Gross Leasable Area | property		150,038
Initial cost to the Company, Land		$ 9,143,000
Initial cost to the Company, Building and Improvements		30,893,000
Subsequent cost capitalized	[1]	3,376,000
Gross carrying amount of Land		9,398,000
Gross carrying amount of building and improvements		34,014,000
SEC Schedule III, Real Estate, Gross, Total		43,412,000
Accumulated Depreciation		$ 4,169,000
East River Park [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1946
East River Park [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1996
Elmhurst Square [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2006
Percent Owned		100.00%
Gross Leasable Area | property		66,254
Initial cost to the Company, Land		$ 1,371,000
Initial cost to the Company, Building and Improvements		5,994,000
Subsequent cost capitalized	[1]	829,000
Gross carrying amount of Land		1,371,000
Gross carrying amount of building and improvements		6,823,000
SEC Schedule III, Real Estate, Gross, Total		8,194,000
Accumulated Depreciation		$ 2,158,000
Elmhurst Square [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1961
Elmhurst Square [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1983
Fairview Commons [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Gross Leasable Area | property		52,964
Initial cost to the Company, Land		$ 858,000
Initial cost to the Company, Building and Improvements		3,568,000
Subsequent cost capitalized	[1]	376,000
Gross carrying amount of Land		858,000
Gross carrying amount of building and improvements		3,944,000
SEC Schedule III, Real Estate, Gross, Total		4,802,000
Accumulated Depreciation		$ 1,160,000
Fairview Commons [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1976
Fairview Commons [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2003
Fieldstone Marketplace [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Percent Owned		100.00%
Gross Leasable Area | property		150,123
Initial cost to the Company, Land		$ 5,229,000
Initial cost to the Company, Building and Improvements		21,440,000
Subsequent cost capitalized	[1]	2,909,000
Gross carrying amount of Land		5,167,000
Gross carrying amount of building and improvements		24,411,000
SEC Schedule III, Real Estate, Gross, Total		29,578,000
Accumulated Depreciation		$ 9,162,000
Fieldstone Marketplace [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Year built/Year last renovated		1988
Fieldstone Marketplace [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2012
Year built/Year last renovated		2003
Fort Washington Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2002
Percent Owned		100.00%
Year built/Year last renovated		2003
Gross Leasable Area | property		41,000
Initial cost to the Company, Land		$ 2,462,000
Subsequent cost capitalized	[1]	5,800,000
Gross carrying amount of Land		2,462,000
Gross carrying amount of building and improvements		5,800,000
SEC Schedule III, Real Estate, Gross, Total		8,262,000
Accumulated Depreciation		$ 2,400,000
Franklin Village Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Percent Owned	[3]	100.00%
Gross Leasable Area | property	[3]	303,524
Initial cost to the Company, Land	[3]	$ 14,270,000
Initial cost to the Company, Building and Improvements	[3]	61,915,000
Subsequent cost capitalized	[1],[3]	4,657,000
Gross carrying amount of Land	[3]	14,681,000
Gross carrying amount of building and improvements	[3]	66,161,000
SEC Schedule III, Real Estate, Gross, Total	[3]	80,842,000
Accumulated Depreciation	[3]	$ 14,743,000
Franklin Village Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired	[3]	2004
Year built/Year last renovated	[3]	1987
Franklin Village Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired	[3]	2012
Year built/Year last renovated	[3]	2005
General Booth Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Year built/Year last renovated		1985
Gross Leasable Area | property		71,639
Initial cost to the Company, Land		$ 1,935,000
Initial cost to the Company, Building and Improvements		9,493,000
Subsequent cost capitalized	[1]	(526,000)
Gross carrying amount of Land		1,935,000
Gross carrying amount of building and improvements		8,967,000
SEC Schedule III, Real Estate, Gross, Total		10,902,000
Accumulated Depreciation		$ 2,950,000
Glen Allen Shopping Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Year built/Year last renovated		2000
Gross Leasable Area | property		63,328
Initial cost to the Company, Land		$ 6,769,000
Initial cost to the Company, Building and Improvements		683,000
Subsequent cost capitalized	[1]	(212,000)
Gross carrying amount of Land		5,367,000
Gross carrying amount of building and improvements		1,873,000
SEC Schedule III, Real Estate, Gross, Total		7,240,000
Accumulated Depreciation		$ 617,000
Gold Star Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2006
Percent Owned		100.00%
Year built/Year last renovated		1988
Gross Leasable Area | property		71,720
Initial cost to the Company, Land		$ 1,644,000
Initial cost to the Company, Building and Improvements		6,519,000
Subsequent cost capitalized	[1]	655,000
Gross carrying amount of Land		1,644,000
Gross carrying amount of building and improvements		7,174,000
SEC Schedule III, Real Estate, Gross, Total		8,818,000
Accumulated Depreciation		$ 3,011,000
Golden Triangle [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Gross Leasable Area | property		202,790
Initial cost to the Company, Land		$ 2,320,000
Initial cost to the Company, Building and Improvements		9,713,000
Subsequent cost capitalized	[1]	9,584,000
Gross carrying amount of Land		2,320,000
Gross carrying amount of building and improvements		19,297,000
SEC Schedule III, Real Estate, Gross, Total		21,617,000
Accumulated Depreciation		$ 9,120,000
Golden Triangle [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1960
Golden Triangle [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2005
Groton Shopping Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Year built/Year last renovated		1969
Gross Leasable Area | property		130,264
Initial cost to the Company, Land		$ 3,070,000
Initial cost to the Company, Building and Improvements		12,320,000
Subsequent cost capitalized	[1]	8,510,000
Gross carrying amount of Land		3,113,000
Gross carrying amount of building and improvements		20,787,000
SEC Schedule III, Real Estate, Gross, Total		23,900,000
Accumulated Depreciation		$ 5,072,000
Halifax Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Year built/Year last renovated		1994
Gross Leasable Area | property		51,510
Initial cost to the Company, Land		$ 1,412,000
Initial cost to the Company, Building and Improvements		5,799,000
Subsequent cost capitalized	[1]	506,000
Gross carrying amount of Land		1,347,000
Gross carrying amount of building and improvements		6,370,000
SEC Schedule III, Real Estate, Gross, Total		7,717,000
Accumulated Depreciation		$ 2,707,000
Hamburg Square [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2004
Percent Owned		100.00%
Gross Leasable Area | property		99,580
Initial cost to the Company, Land		$ 1,153,000
Initial cost to the Company, Building and Improvements		4,678,000
Subsequent cost capitalized	[1]	5,590,000
Gross carrying amount of Land		1,153,000
Gross carrying amount of building and improvements		10,268,000
SEC Schedule III, Real Estate, Gross, Total		11,421,000
Accumulated Depreciation		$ 3,589,000
Hamburg Square [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1993
Hamburg Square [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2010
Jordan Lane [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Gross Leasable Area | property		177,504
Initial cost to the Company, Land		$ 4,291,000
Initial cost to the Company, Building and Improvements		21,176,000
Subsequent cost capitalized	[1]	796,000
Gross carrying amount of Land		4,291,000
Gross carrying amount of building and improvements		21,972,000
SEC Schedule III, Real Estate, Gross, Total		26,263,000
Accumulated Depreciation		$ 7,270,000
Jordan Lane [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1969
Jordan Lane [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1991
Kempsville Crossing [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Gross Leasable Area | property		79,512
Initial cost to the Company, Land		$ 2,207,000
Initial cost to the Company, Building and Improvements		11,000,000
Subsequent cost capitalized	[1]	(3,087,000)
Gross carrying amount of Land		2,207,000
Gross carrying amount of building and improvements		7,913,000
SEC Schedule III, Real Estate, Gross, Total		10,120,000
Accumulated Depreciation		$ 2,898,000
Kempsville Crossing [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1985
Kempsville Crossing [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2013
Kings Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Gross Leasable Area | property		168,243
Initial cost to the Company, Land		$ 2,413,000
Initial cost to the Company, Building and Improvements		12,604,000
Subsequent cost capitalized	[1]	1,494,000
Gross carrying amount of Land		2,408,000
Gross carrying amount of building and improvements		14,103,000
SEC Schedule III, Real Estate, Gross, Total		16,511,000
Accumulated Depreciation		$ 3,541,000
Kings Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1970
Kings Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1994
Lawndale Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2015
Percent Owned		100.00%
Year built/Year last renovated		1998
Gross Leasable Area | property		92,773
Initial cost to the Company, Land		$ 3,635,000
Initial cost to the Company, Building and Improvements		21,854,000
Subsequent cost capitalized	[1]	687,000
Gross carrying amount of Land		3,635,000
Gross carrying amount of building and improvements		22,541,000
SEC Schedule III, Real Estate, Gross, Total		26,176,000
Accumulated Depreciation		$ 3,409,000
Meadows Marketplace [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Percent Owned		100.00%
Year built/Year last renovated		2005
Gross Leasable Area | property		91,518
Initial cost to the Company, Land		$ 1,914,000
Subsequent cost capitalized	[1]	11,444,000
Gross carrying amount of Land		1,914,000
Gross carrying amount of building and improvements		11,444,000
SEC Schedule III, Real Estate, Gross, Total		13,358,000
Accumulated Depreciation		$ 3,732,000
Meadows Marketplace [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2004
Meadows Marketplace [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2012
Metro Square [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2008
Percent Owned		100.00%
Year built/Year last renovated		1999
Gross Leasable Area | property		71,896
Initial cost to the Company, Land		$ 3,121,000
Initial cost to the Company, Building and Improvements		12,341,000
Subsequent cost capitalized	[1]	(221,000)
Gross carrying amount of Land		5,250,000
Gross carrying amount of building and improvements		9,991,000
SEC Schedule III, Real Estate, Gross, Total		15,241,000
Accumulated Depreciation		$ 3,002,000
Newport Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Year built/Year last renovated		1996
Gross Leasable Area | property		64,489
Initial cost to the Company, Land		$ 1,721,000
Initial cost to the Company, Building and Improvements		7,758,000
Subsequent cost capitalized	[1]	464,000
Gross carrying amount of Land		1,682,000
Gross carrying amount of building and improvements		8,261,000
SEC Schedule III, Real Estate, Gross, Total		9,943,000
Accumulated Depreciation		$ 3,431,000
New London Mall [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2009
Percent Owned		100.00%
Gross Leasable Area | property		259,566
Initial cost to the Company, Land		$ 14,891,000
Initial cost to the Company, Building and Improvements		24,967,000
Subsequent cost capitalized	[1]	4,345,000
Gross carrying amount of Land		8,807,000
Gross carrying amount of building and improvements		35,396,000
SEC Schedule III, Real Estate, Gross, Total		44,203,000
Accumulated Depreciation		$ 13,073,000
New London Mall [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1967
New London Mall [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1997
Northside Commons [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2008
Percent Owned		100.00%
Year built/Year last renovated		2009
Gross Leasable Area | property		69,136
Initial cost to the Company, Land		$ 3,332,000
Subsequent cost capitalized	[1]	10,011,000
Gross carrying amount of Land		3,379,000
Gross carrying amount of building and improvements		9,964,000
SEC Schedule III, Real Estate, Gross, Total		13,343,000
Accumulated Depreciation		$ 2,344,000
Norwood Shopping Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2006
Percent Owned		100.00%
Gross Leasable Area | property		97,756
Initial cost to the Company, Land		$ 1,874,000
Initial cost to the Company, Building and Improvements		8,453,000
Subsequent cost capitalized	[1]	771,000
Gross carrying amount of Land		1,874,000
Gross carrying amount of building and improvements		9,224,000
SEC Schedule III, Real Estate, Gross, Total		11,098,000
Accumulated Depreciation		$ 2,910,000
Norwood Shopping Center [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1965
Norwood Shopping Center [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2013
Oak Ridge Shopping Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2006
Percent Owned		100.00%
Year built/Year last renovated		2000
Gross Leasable Area | property		38,700
Initial cost to the Company, Land		$ 960,000
Initial cost to the Company, Building and Improvements		4,254,000
Subsequent cost capitalized	[1]	181,000
Gross carrying amount of Land		960,000
Gross carrying amount of building and improvements		4,435,000
SEC Schedule III, Real Estate, Gross, Total		5,395,000
Accumulated Depreciation		$ 1,608,000
Oakland Commons [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Gross Leasable Area | property		90,100
Initial cost to the Company, Land		$ 2,504,000
Initial cost to the Company, Building and Improvements		15,662,000
Subsequent cost capitalized	[1]	(344,000)
Gross carrying amount of Land		2,504,000
Gross carrying amount of building and improvements		15,318,000
SEC Schedule III, Real Estate, Gross, Total		17,822,000
Accumulated Depreciation		$ 5,128,000
Oakland Commons [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1962
Oakland Commons [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2013
Oakland Mills [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Gross Leasable Area | property		58,224
Initial cost to the Company, Land		$ 1,611,000
Initial cost to the Company, Building and Improvements		6,292,000
Subsequent cost capitalized	[1]	646,000
Gross carrying amount of Land		1,611,000
Gross carrying amount of building and improvements		6,938,000
SEC Schedule III, Real Estate, Gross, Total		8,549,000
Accumulated Depreciation		$ 2,762,000
Oakland Mills [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1960
Oakland Mills [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2004
Palmyra Shopping Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Gross Leasable Area | property		111,051
Initial cost to the Company, Land		$ 1,488,000
Initial cost to the Company, Building and Improvements		6,566,000
Subsequent cost capitalized	[1]	1,813,000
Gross carrying amount of Land		1,488,000
Gross carrying amount of building and improvements		8,379,000
SEC Schedule III, Real Estate, Gross, Total		9,867,000
Accumulated Depreciation		$ 3,259,000
Palmyra Shopping Center [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1960
Palmyra Shopping Center [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2012
Pine Grove Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Gross Leasable Area | property		86,089
Initial cost to the Company, Land		$ 2,010,000
Initial cost to the Company, Building and Improvements		6,489,000
Subsequent cost capitalized	[1]	1,028,000
Gross carrying amount of Land		2,010,000
Gross carrying amount of building and improvements		7,517,000
SEC Schedule III, Real Estate, Gross, Total		9,527,000
Accumulated Depreciation		$ 2,836,000
Pine Grove Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2001
Pine Grove Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2002
Port Richmond Village [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2001
Percent Owned		100.00%
Year built/Year last renovated		1988
Gross Leasable Area | property		125,578
Initial cost to the Company, Land		$ 2,942,000
Initial cost to the Company, Building and Improvements		11,769,000
Subsequent cost capitalized	[1]	3,002,000
Gross carrying amount of Land		2,843,000
Gross carrying amount of building and improvements		14,870,000
SEC Schedule III, Real Estate, Gross, Total		17,713,000
Accumulated Depreciation		$ 5,933,000
Senator Square [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2018
Percent Owned		100.00%
Gross Leasable Area | property		61,691
Initial cost to the Company, Building and Improvements		$ 5,327,000
Subsequent cost capitalized	[1]	41,000
Gross carrying amount of building and improvements		5,368,000
SEC Schedule III, Real Estate, Gross, Total		5,368,000
Accumulated Depreciation		$ 186,000
Senator Square [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1946
Senator Square [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2005
Quartermaster Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2014
Percent Owned		100.00%
Year built/Year last renovated		2004
Gross Leasable Area | property		456,602
Initial cost to the Company, Land		$ 37,031,000
Initial cost to the Company, Building and Improvements		54,210,000
Subsequent cost capitalized	[1]	2,020,000
Gross carrying amount of Land		37,031,000
Gross carrying amount of building and improvements		56,230,000
SEC Schedule III, Real Estate, Gross, Total		93,261,000
Accumulated Depreciation		$ 8,806,000
River View Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Gross Leasable Area | property		236,217
Initial cost to the Company, Land		$ 9,718,000
Initial cost to the Company, Building and Improvements		40,356,000
Subsequent cost capitalized	[1]	7,138,000
Gross carrying amount of Land		10,872,000
Gross carrying amount of building and improvements		46,340,000
SEC Schedule III, Real Estate, Gross, Total		57,212,000
Accumulated Depreciation		$ 18,100,000
River View Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1991
River View Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1998
San Souci Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2009
Percent Owned		40.00%
Gross Leasable Area | property		264,134
Initial cost to the Company, Land		$ 14,849,000
Initial cost to the Company, Building and Improvements		18,445,000
Subsequent cost capitalized	[1]	5,145,000
Gross carrying amount of Land		13,406,000
Gross carrying amount of building and improvements		25,033,000
SEC Schedule III, Real Estate, Gross, Total		38,439,000
Accumulated Depreciation		$ 11,515,000
San Souci Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1985
San Souci Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1997
Shoppes at Arts District [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2016
Percent Owned		100.00%
Year built/Year last renovated		2011
Gross Leasable Area | property		35,676
Initial cost to the Company, Land		$ 2,247,000
Initial cost to the Company, Building and Improvements		18,616,000
Subsequent cost capitalized	[1]	47,000
Gross carrying amount of Land		2,247,000
Gross carrying amount of building and improvements		18,663,000
SEC Schedule III, Real Estate, Gross, Total		20,910,000
Accumulated Depreciation		$ 1,993,000
South Philadelphia [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Gross Leasable Area | property		251,881
Initial cost to the Company, Land		$ 8,222,000
Initial cost to the Company, Building and Improvements		36,314,000
Subsequent cost capitalized	[1]	8,837,000
Gross carrying amount of Land		10,363,000
Gross carrying amount of building and improvements		43,010,000
SEC Schedule III, Real Estate, Gross, Total		53,373,000
Accumulated Depreciation		$ 17,319,000
South Philadelphia [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1950
South Philadelphia [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2003
Southington Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Gross Leasable Area | property		155,842
Initial cost to the Company, Building and Improvements		$ 11,834,000
Subsequent cost capitalized	[1]	574,000
Gross carrying amount of building and improvements		12,408,000
SEC Schedule III, Real Estate, Gross, Total		12,408,000
Accumulated Depreciation		$ 4,677,000
Southington Center [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1972
Southington Center [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2000
Suffolk Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Year built/Year last renovated		1984
Gross Leasable Area | property		67,216
Initial cost to the Company, Land		$ 1,402,000
Initial cost to the Company, Building and Improvements		7,236,000
Subsequent cost capitalized	[1]	(1,271,000)
Gross carrying amount of Land		1,402,000
Gross carrying amount of building and improvements		5,965,000
SEC Schedule III, Real Estate, Gross, Total		7,367,000
Accumulated Depreciation		$ 2,006,000
Swede Square [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Gross Leasable Area | property		100,816
Initial cost to the Company, Land		$ 2,268,000
Initial cost to the Company, Building and Improvements		6,232,000
Subsequent cost capitalized	[1]	6,118,000
Gross carrying amount of Land		2,272,000
Gross carrying amount of building and improvements		12,346,000
SEC Schedule III, Real Estate, Gross, Total		14,618,000
Accumulated Depreciation		$ 5,612,000
Swede Square [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1980
Swede Square [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2012
The Brickyard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2004
Percent Owned		100.00%
Gross Leasable Area | property		227,598
Initial cost to the Company, Land		$ 7,632,000
Initial cost to the Company, Building and Improvements		29,308,000
Subsequent cost capitalized	[1]	4,329,000
Gross carrying amount of Land		7,648,000
Gross carrying amount of building and improvements		33,621,000
SEC Schedule III, Real Estate, Gross, Total		41,269,000
Accumulated Depreciation		$ 11,008,000
The Brickyard [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1990
The Brickyard [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2012
The Commons [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2004
Percent Owned		100.00%
Year built/Year last renovated		2003
Gross Leasable Area | property		203,309
Initial cost to the Company, Land		$ 3,098,000
Initial cost to the Company, Building and Improvements		14,047,000
Subsequent cost capitalized	[1]	3,490,000
Gross carrying amount of Land		3,098,000
Gross carrying amount of building and improvements		17,537,000
SEC Schedule III, Real Estate, Gross, Total		20,635,000
Accumulated Depreciation		$ 5,737,000
The Point [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2000
Percent Owned		100.00%
Gross Leasable Area | property		268,037
Initial cost to the Company, Land		$ 2,700,000
Initial cost to the Company, Building and Improvements		10,800,000
Subsequent cost capitalized	[1]	14,981,000
Gross carrying amount of Land		2,996,000
Gross carrying amount of building and improvements		25,485,000
SEC Schedule III, Real Estate, Gross, Total		28,481,000
Accumulated Depreciation		$ 10,611,000
The Point [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1972
The Point [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2012
The Shops at Bloomfield Station [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2016
Percent Owned		100.00%
Year built/Year last renovated		2015
Gross Leasable Area | property		63,844
Initial cost to the Company, Land		$ 625,000
Initial cost to the Company, Building and Improvements		17,674,000
Subsequent cost capitalized	[1]	177,000
Gross carrying amount of Land		625,000
Gross carrying amount of building and improvements		17,851,000
SEC Schedule III, Real Estate, Gross, Total		18,476,000
Accumulated Depreciation		$ 1,560,000
The Shops at Suffolk Downs [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Gross Leasable Area | property		121,320
Initial cost to the Company, Land		$ 7,580,000
Initial cost to the Company, Building and Improvements		11,089,000
Subsequent cost capitalized	[1]	10,076,000
Gross carrying amount of Land		7,580,000
Gross carrying amount of building and improvements		21,165,000
SEC Schedule III, Real Estate, Gross, Total		28,745,000
Accumulated Depreciation		$ 6,723,000
The Shops at Suffolk Downs [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2005
The Shops at Suffolk Downs [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2011
Timpany Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Gross Leasable Area | property		183,775
Initial cost to the Company, Land		$ 3,412,000
Initial cost to the Company, Building and Improvements		19,240,000
Subsequent cost capitalized	[1]	1,811,000
Gross carrying amount of Land		3,368,000
Gross carrying amount of building and improvements		21,095,000
SEC Schedule III, Real Estate, Gross, Total		24,463,000
Accumulated Depreciation		$ 5,767,000
Timpany Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1970
Timpany Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1989
Trexler Mall [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2005
Percent Owned		100.00%
Gross Leasable Area | property		337,297
Initial cost to the Company, Land		$ 6,932,000
Initial cost to the Company, Building and Improvements		32,815,000
Subsequent cost capitalized	[1]	8,394,000
Gross carrying amount of Land		6,932,000
Gross carrying amount of building and improvements		41,209,000
SEC Schedule III, Real Estate, Gross, Total		48,141,000
Accumulated Depreciation		$ 14,428,000
Trexler Mall [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1973
Trexler Mall [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2013
Trexlertown Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2006
Percent Owned		100.00%
Gross Leasable Area | property		325,171
Initial cost to the Company, Land		$ 13,349,000
Initial cost to the Company, Building and Improvements		23,867,000
Subsequent cost capitalized	[1]	30,109,000
Gross carrying amount of Land		13,351,000
Gross carrying amount of building and improvements		53,974,000
SEC Schedule III, Real Estate, Gross, Total		67,325,000
Accumulated Depreciation		$ 11,592,000
Trexlertown Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1990
Trexlertown Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2011
Valley Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2003
Percent Owned		100.00%
Gross Leasable Area | property		190,939
Initial cost to the Company, Land		$ 1,950,000
Initial cost to the Company, Building and Improvements		7,766,000
Subsequent cost capitalized	[1]	1,620,000
Gross carrying amount of Land		1,950,000
Gross carrying amount of building and improvements		9,386,000
SEC Schedule III, Real Estate, Gross, Total		11,336,000
Accumulated Depreciation		$ 3,853,000
Valley Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1975
Valley Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1994
Washington Center Shoppes [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2001
Percent Owned		100.00%
Gross Leasable Area | property		157,394
Initial cost to the Company, Land		$ 2,061,000
Initial cost to the Company, Building and Improvements		7,314,000
Subsequent cost capitalized	[1]	5,079,000
Gross carrying amount of Land		2,000,000
Gross carrying amount of building and improvements		12,454,000
SEC Schedule III, Real Estate, Gross, Total		14,454,000
Accumulated Depreciation		$ 5,528,000
Washington Center Shoppes [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1979
Washington Center Shoppes [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1995
Webster Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Gross Leasable Area | property		98,984
Initial cost to the Company, Land		$ 3,551,000
Initial cost to the Company, Building and Improvements		18,412,000
Subsequent cost capitalized	[1]	4,784,000
Gross carrying amount of Land		4,082,000
Gross carrying amount of building and improvements		22,665,000
SEC Schedule III, Real Estate, Gross, Total		26,747,000
Accumulated Depreciation		$ 5,983,000
Webster Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1960
Webster Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2004
Yorktowne Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year acquired		2007
Percent Owned		100.00%
Gross Leasable Area | property		158,982
Initial cost to the Company, Land		$ 5,940,000
Initial cost to the Company, Building and Improvements		25,505,000
Subsequent cost capitalized	[1]	709,000
Gross carrying amount of Land		5,801,000
Gross carrying amount of building and improvements		26,353,000
SEC Schedule III, Real Estate, Gross, Total		32,154,000
Accumulated Depreciation		$ 9,258,000
Yorktowne Plaza [Member] | Minimum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		1970
Yorktowne Plaza [Member] | Maximum [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year built/Year last renovated		2000
Other [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Percent Owned		100.00%
Initial cost to the Company, Land		$ 1,965,000
Subsequent cost capitalized	[1]	122,000
Gross carrying amount of Land		878,000
Gross carrying amount of building and improvements		1,209,000
SEC Schedule III, Real Estate, Gross, Total		2,087,000
Accumulated Depreciation		$ 34,000

[1] Negative amounts represent write-offs of fully depreciated assets.

[2] At December 31, 2018, the aggregate cost for federal income tax purposes was approximately $34.1 million greater than the Company's recorded values.

[3] Amount of encumbrance totals $47.7 million at December 31, 2018.