Real Estate (Schedule of Transactions Related to Properties Held for Sale/Conveyance) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Real Estate Properties [Line Items]
Gain on Sale/Reversal of Impairment		$ 48,857,000	$ 3,753,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Real Estate Properties [Line Items]
Sales Price		100,723,500	21,928,000
Gain on Sale/Reversal of Impairment		$ 51,753,000	$ 4,396,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Metro Square [Member]
Real Estate Properties [Line Items]
Location			Owings Mills, MD
Date Sold			Jul. 09, 2020
Sales Price			$ 4,288,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Riverview Plaza [Member]
Real Estate Properties [Line Items]
Location	Philadelphia, PA
Date Sold	May 16, 2022
Sales Price	$ 34,000,000
Gain on Sale/Reversal of Impairment	$ (361,000)
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Kempsville Crossing [Member]
Real Estate Properties [Line Items]
Location		Virginia Beach, VA
Date Sold		Feb. 24, 2021
Sales Price		$ 1,300,000
Gain on Sale/Reversal of Impairment		$ 1,047,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Oakland Mills Outparcel Building [Member]
Real Estate Properties [Line Items]
Location			Columbia, MD
Date Sold			Sep. 17, 2020
Sales Price			$ 1,050,000
Gain on Sale/Reversal of Impairment			$ 643,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | The Commons [Member]
Real Estate Properties [Line Items]
Location		Dubois, PA
Date Sold		May 05, 2021
Sales Price		$ 9,761,000
Gain on Sale/Reversal of Impairment		$ 1,849,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Glen Allen Shopping Center [Member]
Real Estate Properties [Line Items]
Location			Glen Allen, VA
Date Sold			Oct. 08, 2020
Sales Price			$ 8,540,000
Gain on Sale/Reversal of Impairment			$ 1,780,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Camp Hill Shopping Center [Member]
Real Estate Properties [Line Items]
Location		Camp Hill, PA
Date Sold		Jun. 21, 2021
Sales Price		$ 89,662,500
Gain on Sale/Reversal of Impairment		$ 48,857,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Pine Grove Plaza Outparcel Building [Member]
Real Estate Properties [Line Items]
Location			Brown Mills, NJ
Date Sold			Nov. 02, 2020
Sales Price			$ 1,100,000
Gain on Sale/Reversal of Impairment			$ 565,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Suffolk Plaza [Member]
Real Estate Properties [Line Items]
Location			Suffolk, VA
Date Sold			Dec. 10, 2020
Sales Price			$ 6,950,000
Gain on Sale/Reversal of Impairment			$ 1,408,000