Commitments and Contingencies (Detail)	9 Months Ended
	Sep. 30, 2020 USD ($) tenant	Dec. 31, 2019 USD ($)	Feb. 25, 2014 USD ($)
Commitments And Contingencies [Line Items]
Estimated remediation costs			$ 1,300,000
Escrow deposit			1,400,000
Holdback Escrow seller funded			1,300,000
Holdback Escrow buyer funded			100,000
Maximum seller liability remedian costs			$ 1,300,000
Commitments for tenant improvements and construction work	$ 33,400,000
Cash, FDIC Insured Amount	$ 250,000
Customer Concentration Risk | Base Rent
Commitments And Contingencies [Line Items]
Number of major tenants | tenant	0
Customer Concentration Risk | Total Rental Revenues
Commitments And Contingencies [Line Items]
Concentration risk, percentage	5.00%
Accounts Payable and Accrued Liabilities
Commitments And Contingencies [Line Items]
Contingent liability	$ (500,000)	$ (600,000)
Other Assets
Commitments And Contingencies [Line Items]
Indemnification asset	$ 500,000	$ 600,000