Notes Payable, Bank Credit Facility, Interest and Amortization of Deferred Debt Costs - Narrative (Details)		9 Months Ended
	Mar. 08, 2023 USD ($)	Sep. 30, 2023 USD ($)	Oct. 01, 2030	Oct. 01, 2027	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Aug. 23, 2022 USD ($) swap
Debt Instrument [Line Items]
Revolving credit facility payable, net		$ 249,521,000				$ 161,941,000
Number of interest rate swaps | swap							2
Construction loan payable, net		50,760,000				0
Long-term debt		1,343,312,000
Principal amount		1,360,376,000				1,240,000,000
Debt outstanding with fixed-rate		1,110,000,000				1,070,000,000.00
Debt outstanding with variable-rate		251,000,000				164,000,000
Carrying value of properties collateralizing mortgage notes		1,360,000,000				1,040,000,000.00
Unamortized deferred debt costs		17,064,000				15,800,000
Debt issuance costs amortization		9,700,000				7,900,000
Interest rate swaps
Debt Instrument [Line Items]
Derivative asset		6,600,000
Twinbrook Quarter
Debt Instrument [Line Items]
Long-term debt		53,300,000
Unamortized deferred debt costs						2,700,000
Avenel Business Park
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure		6,300,000
Hampden House
Debt Instrument [Line Items]
Unamortized deferred debt costs		$ 2,900,000				$ 3,000,000
Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Interest rate spread on LIBOR		0.10%
Revolving Credit Facility | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Interest rate spread on LIBOR		1.40%
Term Facility | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Interest rate spread on LIBOR		1.35%
Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity		$ 110,500,000
Revolving credit facility payable, net		351,000,000
Letter of Credit
Debt Instrument [Line Items]
Revolving credit facility payable, net		185,000
Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		525,000,000
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		425,000,000
Line of Credit | Term Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 100,000,000
Line of credit facility, extension term		1 year
Line of Credit | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility payable, net		$ 251,000,000
Secured Debt | Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity							$ 100,000,000
Secured Debt | Term Loan | Agreement Ending October 1, 2030
Debt Instrument [Line Items]
Derivative, notional amount							50,000,000
Secured Debt | Term Loan | Agreement Ending October 1, 2027
Debt Instrument [Line Items]
Derivative, notional amount							$ 50,000,000
Secured Debt | Secured Overnight Financing Rate (SOFR) | Term Loan | Agreement Ending October 1, 2030 | Forecast
Debt Instrument [Line Items]
Derivative, fixed interest rate (as a percent)			2.91%
Secured Debt | Secured Overnight Financing Rate (SOFR) | Term Loan | Agreement Ending October 1, 2027 | Forecast
Debt Instrument [Line Items]
Derivative, fixed interest rate (as a percent)				2.96%
Mortgages
Debt Instrument [Line Items]
Repayments of debt	$ 9,300,000
Mortgages | BJ’s Wholesale Club
Debt Instrument [Line Items]
Long-term debt, term	10 years
Debt instrument, face amount	$ 15,300,000
Debt instrument, interest rate, stated percentage	6.07%
Debt instrument, periodic payment	$ 99,200
Amortization period	25 years
Debt instrument, payment at maturity	$ 11,700,000
Mortgages | Kentlands Place Mortgage
Debt Instrument [Line Items]
Long-term debt		27,500,000
Mortgages | The Waycroft Mortgage
Debt Instrument [Line Items]
Long-term debt		150,000,000
Guarantor obligations, maximum exposure		23,600,000
Mortgages | Ashbrook Marketplace Mortgage
Debt Instrument [Line Items]
Long-term debt		20,400,000
Mortgages | Avenel Business Park
Debt Instrument [Line Items]
Long-term debt		21,900,000
Construction Loans | Construction-to-Permanent Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 145,000,000
Construction loan payable, net		$ 50,800,000