Subsequent events (Details) - USD ($) $ / shares in Units, $ in Thousands						3 Months Ended
	Mar. 04, 2019	Feb. 08, 2019	May 03, 2018	Nov. 10, 2016	Sep. 04, 2014	Jan. 31, 2019
Employee Stock Option [Member]
Subsequent Event [Line Items]
Plan term			10 years	10 years	10 years	10 years
Vesting term			5 years	5 years	5 years	5 years
Options granted during period			38,000	38,000	246,000
Options granted during period, price per share			$ 15.50	$ 21.00	$ 18.45
Subsequent Event [Member] | Employee Stock Option [Member]
Subsequent Event [Line Items]
Plan term	10 years
Vesting term	5 years
Options granted during period	5,000
Options granted during period, price per share	$ 15.00
Subsequent Event [Member] | Pathmark supermarket in Patchogue [Member]
Subsequent Event [Line Items]
Agreed sales price of property held for sale		$ 7,500
Rental properties		6,200
Capital gain		800
Net cash proceeds from sale of property		2,000
Mortgage payoff		5,200
Sale of property operating loss		$ 800
Price per share operating loss eliminated from sale of property		$ 0.12