Interest rate swap contracts (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 29, 2016	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Oct. 31, 2016	Apr. 22, 2016	Dec. 26, 2012
Mortgages and construction loan payable		$ 324,558,000		$ 324,558,000		$ 329,719,000
Interest rate swap contract assets		1,314,000		1,314,000		91,000
Net unrealized gain (loss) on interest rate swap contracts		(88,000)	$ (774,000)	2,518,000	$ (1,615,000)	(725,000)
Interest rate swap contract liabilities		587,000		$ 587,000		1,882,000
Basis points, interest rate				1.75%
Wayne PSC swap [Member]
Interest rate swap contract assets		1,177,000		$ 1,177,000		91,000
Damascus Centre Swap [Member]
Interest rate swap contract assets		137,000		137,000
Interest rate swap contract liabilities						521,000
Regency Swap [Member]
Interest rate swap contract liabilities		587,000		587,000		$ 1,361,000
Wayne PSC, LLC Loan [Member]
Refinanced loan amount	$ 24,200,000
Loan amount		25,300,000		25,300,000
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		25,300,000		25,300,000
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	20,500,000		20,500,000
Mortgages and construction loan payable							$ 2,320,000
Notional amount of interest rate swap		$ 20,500,000		$ 20,500,000
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]
Loan amount							2,320,000
Fixed interest rate		3.53%		3.53%
Basis points, interest rate				2.10%
Amount of loan readily available							470,000
Amount of loan held in escrow							$ 1,850,000
Maturity date of loan				Jan. 03, 2023
Provident Bank [Member]
Loan amount		$ 16,200,000		$ 16,200,000
Notional amount of interest rate swap		$ 16,200,000		$ 16,200,000
Fixed interest rate		3.75%		3.75%
Basis points, interest rate				1.25%
Maturity date of loan				Dec. 15, 2024