Revolving Credit Agreement (Details) - Webster Credit Line $ in Thousands	3 Months Ended	6 Months Ended	66 Months Ended
	May 31, 2018 USD ($) ft²	May 31, 2018 USD ($) ft²	May 31, 2018 USD ($) ft²
Revolving credit agreement
Maximum borrowing capacity	$ 15,000	$ 15,000	$ 15,000
Extension period	1 year
Proceeds from Lines of Credit			0
Standby letters of credit aggregate amount	$ 1,068	$ 1,068	$ 1,068
Griffin Center South, Bloomfield, CT
Revolving credit agreement
Area of collateralized properties (in square feet) | ft²	235,000	235,000	235,000
Single-story office building in Griffin Center
Revolving credit agreement
Area of collateralized properties (in square feet) | ft²	48,000	48,000	48,000
LIBOR
Revolving credit agreement
Variable interest rate margin (as a percent)		2.75%