Notes Payable, Revolving Credit Facility, Interest and Amortization of Deferred Debt Costs - Narrative (Details) - USD ($)			3 Months Ended
	Mar. 31, 2022	Mar. 11, 2022	Mar. 31, 2022	Mar. 31, 2021	Feb. 23, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Revolving credit facility payable	$ 135,360,000		$ 135,360,000			$ 103,167,000
Repayments of secured debt			36,473,000	$ 13,553,000
Principal amount	1,139,855,000		1,139,855,000
Principal amount	1,150,552,000		1,150,552,000			1,200,000,000
Debt outstanding with fixed-rate	912,600,000		912,600,000			949,000,000
Debt outstanding with variable-rate	238,000,000		238,000,000			206,000,000
Carrying value of properties collateralizing mortgage notes	1,100,000,000		1,100,000,000			1,100,000,000
Unamortized deferred debt costs	10,697,000		10,697,000			11,200,000
Debt issuance costs amortization	7,700,000		7,700,000			$ 7,700,000
Broadlands Village Mortgage
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure	3,700,000		3,700,000
Principal amount	29,500,000		29,500,000
Avenel Business Park
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure	6,300,000		6,300,000
The Waycroft Mortgage
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure	$ 23,600,000		23,600,000
Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Interest rate spread on LIBOR	1.35%
Term Facility | LIBOR
Debt Instrument [Line Items]
Interest rate spread on LIBOR	1.30%
Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity	$ 233,500,000		233,500,000
Revolving credit facility payable	238,000,000		238,000,000
Letter of Credit
Debt Instrument [Line Items]
Revolving credit facility payable	185,000		185,000
Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	525,000,000		525,000,000
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	425,000,000		425,000,000
Line of Credit | Term Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	100,000,000		100,000,000
Line of Credit | Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility payable	138,000,000		$ 138,000,000
Secured Debt | Construction-to-Permanent Loan
Debt Instrument [Line Items]
Debt instrument, face amount					$ 133,000,000
Debt instrument, interest rate, stated percentage					3.90%
Amortization period			25 years
Mortgages | Lansdowne Town Center Mortgage
Debt Instrument [Line Items]
Repayments of secured debt		$ 28,300,000
Mortgages | Avenel Business Park
Debt Instrument [Line Items]
Principal amount	23,800,000		$ 23,800,000
Mortgages | The Waycroft Mortgage
Debt Instrument [Line Items]
Principal amount	155,200,000		155,200,000
Mortgages | Ashbrook Marketplace Mortgage
Debt Instrument [Line Items]
Principal amount	21,200,000		21,200,000
Mortgages | Kentlands Place Mortgage
Debt Instrument [Line Items]
Principal amount	$ 28,800,000		$ 28,800,000