Mortgage Notes Payable - Additional Information (Detail)								12 Months Ended
	Mar. 15, 2024 USD ($) Item	Jul. 31, 2023 USD ($) Item	Aug. 05, 2022 USD ($) Property	Mar. 24, 2020 USD ($) Item	Mar. 21, 2018 USD ($) Item	Dec. 20, 2017 USD ($) Item Property	Mar. 13, 2015 USD ($)	Dec. 31, 2024 USD ($) Property	Dec. 31, 2023 USD ($)	Dec. 31, 2014 USD ($) ft²	Oct. 15, 2024 USD ($)
Debt Instrument [Line Items]
Amortization of deferred mortgage loan costs								$ 1,700,000	$ 1,300,000
Mortgage notes payable								486,822,000	379,187,000
Number of wholly-owned subsidiaries of the UPREIT | Item	3	3		2	4	4
People's United Bank [Member]
Debt Instrument [Line Items]
Mortgage notes payable											$ 14,400,000
3.45% Transamerica Life Insurance Company, Loan [Member]
Debt Instrument [Line Items]
Mortgage notes payable				$ 8,400,000				$ 7,809,000	8,037,000
Permanent financing interest rate				3.45%
Permanent financing period				10 years
Debt instrument, payment terms								principal balance of the note until April 1, 2022, and (ii) principal and interest payments (amortized over a 25-year period commencing at the end of the interest-only period) from May 1, 2022 through March 1, 2030. The entire principal balance of each note is due and payable on April 1, 2030, the loan maturity date
Interest Rate								3.45%
Maturity								Apr. 01, 2030
3.45% Transamerica Life Insurance Company, Loan [Member] | Event of Default [Member]
Debt Instrument [Line Items]
Event of default, description								If a default exists, the outstanding principal balance of the notes shall, at the option of the lender, bear interest at a rate equal to the lesser of (i) 10% per annum over the note rate and (ii) the highest rate of interest permitted to be paid or collected by applicable law with respect to the loan.
3.45% Transamerica Life Insurance Company, Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Loan Prepayment Premium Percentage,upon providing advance notice of prepayment				1.00%
4.25 % United States Life Insurance Company, Loan [Member]
Debt Instrument [Line Items]
Mortgage notes payable					$ 33,000,000.0			$ 32,059,000	32,632,000
Permanent financing interest rate					4.25%
Permanent financing period					10 years
Debt instrument, payment terms								the principal balance for the first five (5) years of the term and principal and interest payments (amortized over a 30-year period) during the second five years of the term. The entire principal balance is due and payable on April 1, 2028, the loan maturity date.
Interest Rate								4.25%
Maturity								Apr. 01, 2028
3.82 % United States Life Insurance Company, Loan [Member]
Debt Instrument [Line Items]
Mortgage notes payable						$ 39,000,000.0		$ 39,000,000	39,000,000
Permanent financing period						10 years
Debt instrument, payment terms								During the period from February 1, 2018 to December 1, 2027, payments of interest only on the principal balance of the U.S. Life Note (as defined below) will be payable in arrears, with the entire principal balance due and payable on January 1, 2028, the loan maturity date.
Number of collateralized properties | Property						4
Interest Rate						3.82%		3.82%
Maturity						Jan. 01, 2028		Jan. 01, 2028
Application fee to lender						$ 50,000
Event of default, description								In the event of default, the initial rate of interest on the U.S. Life Note will increase to the greatest of (i) 18% per annum, (ii) a per annum rate equal to 4% over the prime established rate, or (iii) a per annum rate equal to 5% over the original interest rate, all subject to the applicable state or federal laws.
3.82 % United States Life Insurance Company, Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Loan Prepayment Premium Percentage,upon providing advance notice of prepayment						1.00%
3.82 % United States Life Insurance Company, Loan [Member] | Minimum [Member] | Event of Default [Member]
Debt Instrument [Line Items]
Increase in debt instrument interest rate upon default						18.00%
American International Group 2022, Loan [Member]
Debt Instrument [Line Items]
Mortgage notes payable								$ 225,000,000	225,000,000
Interest Rate								4.63%
Maturity								Sep. 01, 2032
Transamerica Life Insurance Company 2023, Loan [Member]
Debt Instrument [Line Items]
Mortgage notes payable		$ 25,000,000						$ 25,000,000	25,000,000
Permanent financing interest rate		5.40%
Permanent financing period		10 years
Debt instrument, payment terms								principal balance of the note until August 1, 2026, and (ii) principal and interest payments (amortized over a 30-year period commencing at the end of the interest-only period) from September 1, 2026 through July 1, 2033. The entire principal balance of each note is due and payable on August 1, 2033, the loan maturity date.
Interest Rate								5.40%
Maturity								Aug. 01, 2033
Transamerica Life Insurance Company 2023, Loan [Member] | Event of Default [Member]
Debt Instrument [Line Items]
Event of default, description								If a default exists, the outstanding principal balance of the notes shall, at the option of the lender, bear interest at a rate equal to the lesser of (i) 10% per annum over the note rate and (ii) the highest rate of interest permitted to be paid or collected by applicable law with respect to the loan.
Transamerica Life Insurance Company 2023, Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Loan Prepayment Premium Percentage,upon providing advance notice of prepayment		1.00%
Allstate Life Insurance Company, Loan [Member]
Debt Instrument [Line Items]
Mortgage notes payable								$ 33,945,000	$ 34,808,000
Interest Rate								4.00%
Maturity								Apr. 01, 2025
American General Life Insurance Company [Member]
Debt Instrument [Line Items]
Mortgage notes payable	$ 125,000,000
Permanent financing period	7 years
Payment term based on amortization schedule	30 years
Debt instrument, payment terms								The loan is a seven-year term loan that requires payments based on a 30-year amortization schedule at the rate of 6.12% per annum with the entire principal balance plus any accrued and unpaid interest due and payable on April 1, 2031
Interest Rate	6.12%
Debt instrument, principal amount	$ 90,000,000
American General Life Insurance Company [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount	50,000,000
American General Life Insurance Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 40,000,000
American General Life Insurance Company [Member] | Minimum [Member]
Debt Instrument [Line Items]
Loan Prepayment Premium Percentage,upon providing advance notice of prepayment	1.00%
Prime Rate [Member] | 3.82 % United States Life Insurance Company, Loan [Member] | Event of Default [Member]
Debt Instrument [Line Items]
Debt instrument Interest rate upon default						4.00%
Original Interest Rate [Member] | 3.82 % United States Life Insurance Company, Loan [Member] | Event of Default [Member]
Debt Instrument [Line Items]
Debt instrument interest rate over original interest rate upon default						5.00%
Note Rate [Member] | 3.45% Transamerica Life Insurance Company, Loan [Member] | Event of Default [Member]
Debt Instrument [Line Items]
Debt instrument Interest rate upon default				10.00%
Note Rate [Member] | Transamerica Life Insurance Company 2023, Loan [Member] | Event of Default [Member]
Debt Instrument [Line Items]
Debt instrument Interest rate upon default		10.00%
Piscataway, NJ [Member]
Debt Instrument [Line Items]
Number of properties acquired | Property								6
Piscataway, NJ [Member] | Allstate Life Insurance Company, Loan [Member]
Debt Instrument [Line Items]
Mortgage notes payable								$ 39,100,000
Permanent financing period							10 years
Payment term based on amortization schedule							30 years
Debt Instrument, balloon payment due upon maturity							$ 33,700,000
Extension agreement terms period							30 days
Interest Rate							4.00%
Maturity							Apr. 01, 2025
AIG Loan [Member] | American International Group 2022, Loan [Member]
Debt Instrument [Line Items]
Interest Rate			4.63%
Maturity			Sep. 01, 2032
Loan related costs			$ 7,900,000
Prepayment fee			5,100,000
Debt instrument, principal amount			$ 225,000,000
Debt instrument, interest rate terms								monthly interest-only payments
Number of properties secured | Property			25
AIG Loan [Member] | New York [Member] | American International Group 2022, Loan [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount			$ 144,300,000
AIG Loan [Member] | Connecticut And New Jersey | American International Group 2022, Loan [Member]
Debt Instrument [Line Items]
Debt instrument, principal amount			$ 80,700,000
People's United Bank Loan Agreement [Member]
Debt Instrument [Line Items]
Leasable area owned by the company | ft²										84,000
Mortgage notes payable										$ 15,500,000
Permanent financing interest rate										4.18%
Permanent financing period										10 years
Payment term based on amortization schedule										25 years
Debt instrument, payment terms								Payments for the first seven years were interest only. Payments over the remaining three years of the term were based on a 25-year amortization schedule, with a balloon payment of $14.4 million due at maturity
Debt Instrument, balloon payment due upon maturity										$ 14,400,000