Interest rate cap and swap contracts (Details) - USD ($)			1 Months Ended		3 Months Ended		12 Months Ended
	Feb. 07, 2018	Dec. 07, 2017	Oct. 27, 2017	Sep. 29, 2016	Jan. 31, 2019	Jan. 31, 2018	Oct. 31, 2018	Apr. 22, 2016	Dec. 26, 2012
Derivative [Line Items]
Mortgages and construction loan payable					$ 349,417,000		$ 350,504,000
Interest rate swap contract assets					2,076,000		4,434,000
Unrealized gain (loss) on derivatives					(154,000)
Net unrealized gain (loss) on interest rate swap contracts					(2,364,000)	$ 1,631,000	3,113,000
Interest rate swap contract liabilities					160,000
Damascus Centre Swap [Member]
Derivative [Line Items]
Interest rate swap contract assets					502,000
Wayne PSC swap [Member]
Derivative [Line Items]
Interest rate swap contract assets					1,569,000
Regency Swap [Member]
Derivative [Line Items]
Interest rate swap contract liabilities					86,000
Monmouth swap [Member]
Derivative [Line Items]
Interest rate swap contract assets					74,000		460,000
Station Place on Monmouth, LLC [Member]
Derivative [Line Items]
Percentage of acquisition		100.00%
Wells Fargo Bank [Member]
Derivative [Line Items]
Loan amount	$ 115,300,000
Aareal Capital Corporation [Member]
Derivative [Line Items]
Loan amount	118,500,000
Available to draw	$ 3,380,000
Basis points, interest rate	2.85%
Maturity date of loan	Feb. 06, 2021
Grande Rotunda LLC [Member]
Derivative [Line Items]
Loan amount					118,500,000
Unrealized gain (loss) on derivatives					(154,000)
Interest rate cap asset					5,000
Grande Rotunda LLC Loan [Member]
Derivative [Line Items]
Loan amount					118,500,000
Notional amount of interest rate swap					$ 121,900,000
Fixed interest rate					3.00%
Maturity date of cap					Mar. 05, 2020
Provident Bank [Member]
Derivative [Line Items]
Refinanced loan amount					$ 16,200,000
Loan amount		$ 12,350,000			15,800,000
Notional amount of interest rate swap		$ 12,350,000			$ 15,800,000
Fixed interest rate		4.35%			3.75%
Basis points, interest rate		1.80%	2.75%		1.25%
Maturity date of loan		Dec. 15, 2027	Oct. 31, 2022		Dec. 15, 2024
Wayne PSC, LLC Loan [Member]
Derivative [Line Items]
Refinanced loan amount				$ 24,200,000
Loan amount					$ 24,300,000
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					24,300,000
Fixed interest rate				3.625%
Basis points, interest rate				2.20%
People's United Bank [Member]
Derivative [Line Items]
Loan amount				$ 25,800,000	19,700,000
Mortgages and construction loan payable								$ 2,320,000
Notional amount of interest rate swap					$ 19,800,000
People's United Bank [Member] | Tranche One [Member]
Derivative [Line Items]
Loan amount									$ 20,000,000
Fixed interest rate					3.81%
Basis points, interest rate					2.10%
Maturity date of loan					Jan. 03, 2023
People's United Bank [Member] | Tranche Two [Member]
Derivative [Line Items]
Fixed interest rate					3.53%
Damascus Centre [Member]
Derivative [Line Items]
Interest rate swap contract assets							955,000
Wayne PSC swap [Member]
Derivative [Line Items]
Interest rate swap contract assets							2,452,000
Regency Swap [Member]
Derivative [Line Items]
Interest rate swap contract assets							$ 408,000