Interest rate swap contracts (Details) - USD ($)		1 Months Ended	2 Months Ended	3 Months Ended		12 Months Ended
	Dec. 07, 2017	Sep. 29, 2016	Jan. 31, 2018	Jan. 31, 2018	Jan. 31, 2017	Oct. 31, 2017	Apr. 22, 2016	Dec. 26, 2012
Mortgages and construction loan payable			$ 353,613,000	$ 353,613,000		$ 323,435,000
Interest rate swap contract assets			2,792,000	2,792,000		1,600,000
Net unrealized gain (loss) on interest rate swap contracts				1,631,000	$ 2,846,000
Interest rate swap contract liabilities						439,000
Basis points, interest rate				0.00%
Damascus Centre Swap [Member]
Interest rate swap contract assets			697,000	$ 697,000
Unrealized gain (loss) on derivatives					$ 2,846,000	2,952,000
Wayne PSC swap [Member]
Interest rate swap contract assets			2,003,000	2,003,000
Regency Swap [Member]
Interest rate swap contract assets			27,000	27,000
Monmouth swap [Member]
Interest rate swap contract assets			65,000	65,000
Provident Bank [Member]
Loan amount	$ 12,350,000		16,200,000	16,200,000
Notional amount of interest rate swap	$ 12,350,000		$ 16,200,000	$ 16,200,000
Fixed interest rate	4.35%		3.75%	3.75%
Basis points, interest rate	1.80%		2.75%	1.25%
Maturity date of loan	Dec. 15, 2027			Dec. 15, 2024
Wayne PSC, LLC Loan [Member]
Refinanced loan amount		$ 24,200,000
Loan amount			$ 24,900,000	$ 24,900,000
Description of loan amendment terms		In order to minimize interest rate volatility during the term of the loan, Wayne PSC, LLC entered into an interest rate swap agreement that, in effect, converted the floating interest rate to a fixed interest rate of 3.625% over the term of the loan.
Notional amount of interest rate swap			25,000,000	25,000,000
Fixed interest rate		3.625%
Basis points, interest rate		2.20%
Maturity date of loan		Oct. 01, 2026
People's United Bank [Member]
Loan amount		$ 25,800,000	20,200,000	20,200,000
Mortgages and construction loan payable							$ 2,320,000
Notional amount of interest rate swap			$ 20,300,000	$ 20,300,000
People's United Bank [Member] | Tranche One [Member]
Loan amount								$ 20,000,000
Fixed interest rate			3.81%	3.81%
Basis points, interest rate				2.10%
Maturity date of loan				Jan. 03, 2023
People's United Bank [Member] | Tranche Two [Member]
Fixed interest rate			3.53%	3.53%
Damascus Centre [Member]
Interest rate swap contract assets						275,000
Wayne PSC swap [Member]
Interest rate swap contract assets						1,325,000
Regency Swap [Member]
Interest rate swap contract liabilities						$ 439,000
Station Place on Monmouth, LLC [Member]
Percentage of acquisition	100.00%