Subsequent Events (Details Narrative) - Subsequent Event [Member]			1 Months Ended
	Aug. 11, 2020 USD ($) properties	Jul. 15, 2020	Jul. 30, 2020 $ / shares	Aug. 07, 2020 USD ($)	Jul. 24, 2020 USD ($)	Jul. 17, 2020 USD ($)	Jul. 08, 2020 USD ($)
Subsequent Event [Line Items]
Current lease renewal and revised USPS lease form, description	The USPS is occupying such properties as a holdover tenant, representing an aggregate annualized rental income of $2.4 million. As of the date of this report, the USPS has not vacated or notified us of its intention to vacate any of these 55 properties.
Acquisition of properties, description	We purchased 98 postal properties for approximately $23.4 million during the period subsequent to June 30, 2020.
Amount of credit facility satisfied | $					$ 42,000,000
Common stock dividend per share | $ / shares			$ 0.205
Common stock dividend paid			Aug. 31, 2020
Common stock dividend record			Aug. 14, 2020
Subsequent acquisitions costs | $	$ 3,700,000
Number of lease properties in holdover that expired in 2018 | properties	1
Number of lease properties in holdover that expired in 2019 | properties	21
Number of lease properties in holdover that expired in 2020 | properties	33
Follow on public offering, description		The Company priced a public offering of 3.5 million shares of its Class A Common Stock (the “Follow-on Offering”) at $13.00 per share. On July 17, 2020, the underwriters purchased an additional 521,840 shares pursuant to a 30-day option to purchase up to an additional 525,000 shares at $13.00 per share (the “Additional Shares”). The Follow-on Offering, including the Additional Shares, closed on July 20, 2020 resulting in $52.2 million in gross proceeds, and approximately $49.4 million in net proceeds after deducting approximately $2.9 million in underwriting discounts and before giving effect to $0.9 million in other estimated expenses relating to the Follow-on Offering.
Amount drawn on credit facility | $	$ 39,500,000			$ 3,000,000		$ 6,500,000	$ 4,500,000