Leases - Additional Information (Details) - Tenant	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Product Information [Line Items]
Number of tenants	4	4
Pratt And Whitney Corporation | Sales Revenue Net | Customer Concentration Risk | Huntsville, AL | Single Tenant Building
Product Information [Line Items]
Concentration risk, percentage	17.30%	20.80%
General Services Administration | Sales Revenue Net | Customer Concentration Risk | Norfolk, VA | Two-Tenant Office Building
Product Information [Line Items]
Concentration risk, percentage	22.90%	26.20%
PRA Holding | Sales Revenue Net | Customer Concentration Risk | Norfolk, VA | Single Tenant Building
Product Information [Line Items]
Concentration risk, percentage	19.90%	22.70%
Maersk Inc | Sales Revenue Net | Customer Concentration Risk | Norfolk, VA | Two-Tenant Office Building
Product Information [Line Items]
Concentration risk, percentage	10.20%	11.10%