Revolving Credit Agreement (Details) $ in Thousands		9 Months Ended
	Sep. 19, 2019 USD ($) ft²	Aug. 31, 2019 USD ($) ft²
Webster Credit Line
Revolving credit agreement
Standby letters of credit aggregate amount		$ 639
Webster Credit Line | Subsequent events
Revolving credit agreement
Maximum borrowing capacity	$ 15,000
Increased line of credit	$ 19,500
Maximum percentage of loan to value	72.00%
Minimum liquidity	$ 5,000
Fixed charge coverage ratio	1.1
Webster Credit Line | Griffin Center South, Bloomfield, CT
Revolving credit agreement
Area of collateralized properties (in square feet) | ft²		235,000
Webster Credit Line | Single-story office building in Griffin Center
Revolving credit agreement
Area of collateralized properties (in square feet) | ft²		48,000
Webster Credit Line | Industrial/warehouse building
Revolving credit agreement
Area of collateralized properties (in square feet) | ft²	31,000
Webster Credit Line | LIBOR
Revolving credit agreement
Variable interest rate margin (as a percent)		2.75%
Webster Credit Line | LIBOR | Subsequent events
Revolving credit agreement
Variable interest rate margin (as a percent)	2.50%
Acquisition Credit Line | Subsequent events
Revolving credit agreement
Maximum borrowing capacity	$ 15,000
Increased line of credit	19,500
Minimum liquidity	$ 5,000
Purchase price of real estate acquisitions (as a percent)	65.00%
Maximum period for obtaining permanent finance from date of drawn	135 days
Minimum debt service coverage ratio	1.25
Minimum net worth	$ 80,000
Percentage of fair market value of assets	50.00%
Acquisition Credit Line | LIBOR | Subsequent events
Revolving credit agreement
Variable interest rate margin (as a percent)	2.75%