Mortgage Loans Payable and Unsecured Credit Facility (Schedule of Debt and Finance Lease Obligations Related to Continuing Operations) (Details) - USD ($)	6 Months Ended
Jun. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Credit facilities	$ 41,000,000	$ 66,000,000
Unamortized issuance costs	(2,848,000)
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facilities	41,000,000.0
Continuing Operations [Member]
Debt Instrument [Line Items]
Total debt gross	504,596,000
Total debt	$ 501,748,000
Weighted average contractual interest rate	3.70%
Continuing Operations [Member] \| Fixed-Rate Mortgage - Held for Sale [Member] \| Franklin Village [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 30, 2026
Total debt gross	$ 44,018,000
Weighted average contractual interest rate	3.90%
Continuing Operations [Member] \| Fixed-Rate Mortgage - Held for Sale [Member] \| Shops at Suffolk Downs [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 30, 2031
Total debt gross	$ 15,600,000
Weighted average contractual interest rate	3.50%
Continuing Operations [Member] \| Fixed-Rate Mortgage - Held for Sale [Member] \| Trexlertown Plaza [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 30, 2031
Total debt gross	$ 36,100,000
Weighted average contractual interest rate	3.50%
Continuing Operations [Member] \| Fixed-Rate Mortgage - Held for Sale [Member] \| The Point [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 30, 2031
Total debt gross	$ 29,700,000
Weighted average contractual interest rate	3.50%
Continuing Operations [Member] \| Fixed-Rate Mortgage - Held for Sale [Member] \| Christina Crossing [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 30, 2031
Total debt gross	$ 17,000,000
Weighted average contractual interest rate	3.50%
Continuing Operations [Member] \| Fixed-Rate Mortgage - Held for Sale [Member] \| Lawndale Plaza [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 30, 2031
Total debt gross	$ 15,600,000
Weighted average contractual interest rate	3.50%
Continuing Operations [Member] \| Finance Lease Obligation - Held for Sale [Member] \| Senator Square Finance Lease Obligation [Member]
Debt Instrument [Line Items]
Maturity date	Sep. 30, 2050
Total debt gross	$ 5,578,000
Weighted average contractual interest rate	5.30%
Continuing Operations [Member] \| Fixed-Rate Mortgage [Member] \| Term Loan [Member] \| Unsecured Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date	Apr. 30, 2023
Credit facilities	$ 100,000,000
Weighted average contractual interest rate	3.30%
Continuing Operations [Member] \| Fixed-Rate Mortgage [Member] \| Term Loan Two [Member] \| Unsecured Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date	Sep. 30, 2024
Credit facilities	$ 75,000,000
Weighted average contractual interest rate	3.80%
Continuing Operations [Member] \| Fixed-Rate Mortgage [Member] \| Term Loan Three [Member] \| Unsecured Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date	Jul. 31, 2025
Credit facilities	$ 75,000,000
Weighted average contractual interest rate	4.70%
Continuing Operations [Member] \| Fixed-Rate Mortgage [Member] \| Term Loan Four [Member] \| Unsecured Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date	Aug. 31, 2026
Credit facilities	$ 50,000,000
Weighted average contractual interest rate	3.30%
Continuing Operations [Member] \| Variable Rate Mortgage [Member] \| Revolving Credit Facility [Member] \| Unsecured Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date	Aug. 31, 2024
Credit facilities	$ 41,000,000
Weighted average contractual interest rate	3.10%
Continuing Operations [Member] \| Fixed-Rate Mortgage and Finance Lease Obligation - Held for Sale [Member]
Debt Instrument [Line Items]
Total debt gross	$ 163,596,000
Weighted average contractual interest rate	3.60%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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-Publisher FASB
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Balance Type:	debit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Balance Type:	credit
Period Type:	instant

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References

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-Publisher FASB
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+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

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