Real Estate (Narrative) (Details)					12 Months Ended
	Mar. 02, 2022 USD ($) property	Oct. 14, 2021 USD ($)	May 05, 2021 USD ($) ft² ShoppingCenter $ / ft²	Jun. 19, 2019 USD ($)	Dec. 31, 2021 USD ($) property	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Real Estate Properties [Line Items]
Number of properties | property					50
Impairment charges					$ 99,888,000	$ 7,607,000	$ 8,938,000
Impairment charges, assets held for use	$ 83,200,000
Impairment charges, assets held for sale	$ 18,500,000
Contributed capital to joint venture					4,654,000
Purchase price							9,083,000
Investment in Unconsolidated Joint Venture [Member]
Real Estate Properties [Line Items]
Area of commercial building | ft²			258,000
Area of commercial space leased percentage			100.00%
Term of lease			20 years 10 months
Number of redevelopment of existing shopping centers | ShoppingCenter			2
Initial term of construction loan			3 years
Percentage of interest in joint venture			10.00%
Development cost sold to Joint Venture			$ 8,000,000.0
Initial annual net rent amount to be paid upon completion of building			$ 5,400,000
Annual escalator percentage to be paid on each anniversary of rent commencement			2.50%
Operating costs, property taxes and amortization of tenant improvements			$ 8,100,000
Annual net rent amount to be paid upon completion of building			$ 13,500,000
Free rent period			10 months
Tenant credit against either annual rent or any other tenant payment obligations including tenant improvement costs, in excess of tenant improvement allowance			$ 6,800,000
Amortized over period			240 months
Investment in Unconsolidated Joint Venture [Member] | Between the 10th and 12th Lease Years [Member]
Real Estate Properties [Line Items]
Additional per rentable square foot tenant improvement allowance to be contributed | $ / ft²			9.38
Investment in Unconsolidated Joint Venture [Member] | Maximum [Member]
Real Estate Properties [Line Items]
Construction financing maximum amount			$ 105,000,000
Joint venture contribution to be made per rentable square foot toward cost of tenant improvements | $ / ft²			155
Investment in Unconsolidated Joint Venture [Member] | LIBOR Rate [Member]
Real Estate Properties [Line Items]
Construction loan initial interest			LIBOR plus 200 basis
Basis spread on borrowings variable rate			200.00%
Investment in Unconsolidated Joint Venture [Member] | Office Space [Member]
Real Estate Properties [Line Items]
Area of commercial building | ft²			240,000
Investment in Unconsolidated Joint Venture [Member] | Street-Level Retail [Member]
Real Estate Properties [Line Items]
Area of commercial building | ft²			18,000
Subsequent Event [Member]
Real Estate Properties [Line Items]
Number of properties | property	33
Proceeds from sale of grocery-anchored shopping centers	$ 840,000,000.0
Aggregate price to backstop redevelopment transaction	80,500,000
Dual-track Strategic Alternatives Process [Member]
Real Estate Properties [Line Items]
Impairment charges					83,200,000
Impairment charges, assets held for sale					18,500,000
Dual-track Strategic Alternatives Process [Member] | Subsequent Event [Member]
Real Estate Properties [Line Items]
Impairment charges	101,700,000
Revelry Redevelopment Project [Member] | Subsequent Event [Member]
Real Estate Properties [Line Items]
Proceeds from sale of grocery-anchored shopping centers	34,000,000.0
Northeast Heights Redevelopment Project [Member] | Subsequent Event [Member]
Real Estate Properties [Line Items]
Proceeds from sale of grocery-anchored shopping centers	46,500,000
Remaining Assets [Member] | Subsequent Event [Member]
Real Estate Properties [Line Items]
Proceeds from sale of grocery-anchored shopping centers	$ 291,300,000
San Souci Plaza [Member]
Real Estate Properties [Line Items]
Minority ownership		60.00%
Purchase price		$ 300,000
Girard Plaza [Member]
Real Estate Properties [Line Items]
Purchase price				$ 8,500,000
Metro Square [Member]
Real Estate Properties [Line Items]
Impairment charges						7,200,000
Real Estate Held for Sale [Member]
Real Estate Properties [Line Items]
Impairment charges						$ 400,000	$ 8,900,000
Reversal of impairment charges					$ 1,800,000