Mortgages payable and credit line (Narrative) (Details) - USD ($)				1 Months Ended				12 Months Ended
	Feb. 07, 2018	Dec. 07, 2017	Jan. 14, 2013	Feb. 28, 2018	Apr. 28, 2017	Sep. 29, 2016	Feb. 01, 2010	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016		Jan. 08, 2018	Nov. 23, 2016	Jun. 30, 2016	Apr. 22, 2016	Dec. 29, 2014
Debt Instrument [Line Items]
Amount drawn on loan								$ 350,504,000	$ 323,435,000
Repayment of mortgages and construction loan								148,680,000	34,254,000	$ 28,314,000
Construction and pre-development costs										$ 13,535,000	[1]
Amount due within five years								36,878,000
Grande Rotunda LLC [Member]
Debt Instrument [Line Items]
Fee amount				$ 900,000
Station Place on Monmouth, LLC [Member]
Debt Instrument [Line Items]
Percentage of acquisition		100.00%
WestFREIT Corp [Member]
Debt Instrument [Line Items]
Refinanced loan amount					$ 22,000,000
Basis points, interest rate					2.75%
Maturity date of loan					Apr. 28, 2019
Net proceeds from refinancing of debt					$ 1,100,000
Description of loan amendment terms					This refinancing resulted in: (i) a reduction in the annual interest rate from a fixed rate of 5.55% to a variable rate
Wells Fargo Bank [Member]
Debt Instrument [Line Items]
Fixed interest rate	3.00%
Amount drawn on loan	$ 115,300,000
Tanant improvements	118,500,000
Leasing costs	$ 3,380,000
Mortgages [Member]
Debt Instrument [Line Items]
Fixed rate mortgage loans								$ 209,274,000	181,757,000
Mortgages [Member] | Rockaway, NJ Mortgage [Member]
Debt Instrument [Line Items]
Fixed interest rate								5.37%
Debt Instrument, Periodic Payment								$ 115,850
Debt Instrument, Collateral Amount								15,590,000
Fixed rate mortgage loans								$ 16,152,000	16,660,000
Mortgages [Member] | Westwood, NJ#1 [Member]
Debt Instrument [Line Items]
Refinanced loan amount			$ 8,000,000
Mortgages [Member] | Westwood, NJ #2 [Member]
Debt Instrument [Line Items]
Fixed interest rate								4.75%
Debt Instrument, Periodic Payment								$ 129,702
Debt Instrument, Collateral Amount								7,359,000
Loan amount								22,750,000
Fixed rate mortgage loans								$ 19,611,000	20,220,000
Mortgages [Member] | Patchogue, NY [Member]
Debt Instrument [Line Items]
Fixed interest rate								4.50%
Debt Instrument, Periodic Payment								$ 19,600
Debt Instrument, Collateral Amount								6,268,000
Fixed rate mortgage loans								$ 5,231,000	5,231,000
Mortgages [Member] | Wayne, NJ Mortgage 1 [Member]
Debt Instrument [Line Items]
Fixed interest rate								6.09%
Debt Instrument, Periodic Payment								$ 121,100
Debt Instrument, Collateral Amount								1,663,000
Fixed rate mortgage loans								$ 17,334,000	17,705,000
Mortgages [Member] | River Edge, NJ Refinanced Mortgage [Member]
Debt Instrument [Line Items]
Fixed interest rate								4.54%
Debt Instrument, Periodic Payment								$ 57,456
Debt Instrument, Collateral Amount								804,000
Loan amount								11,200,000
Mortgages [Member] | Red Bank, NJ Refinanced Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Collateral Amount								$ 19,303,000
Mortgages [Member] | Westwood, NJ #3 [Member]
Debt Instrument [Line Items]
Fixed interest rate								4.62%
Debt Instrument, Periodic Payment								$ 120,752
Debt Instrument, Collateral Amount								9,231,000
Fixed rate mortgage loans								$ 20,134,000	20,628,000
Mortgages [Member] | Wayne, PSC LLC [Member]
Debt Instrument [Line Items]
Refinanced loan amount						$ 24,200,000
Fixed interest rate								3.625%
Membership interest percentage								40.00%
Description of variable interest rate								a reduction in interest rate from 6.04% to 3.625%
Repurchase amount of acquisition loan								$ 400,000
Net proceeds from refinancing of debt								1,000,000
Mortgages [Member] | People's United Bank [Member]
Debt Instrument [Line Items]
Refinanced loan amount								$ 25,800,000
Basis points, interest rate								2.20%
Maturity date of loan								Oct. 01, 2026
Mortgages [Member] | Second Wayne, NJ Mortgage [Member]
Debt Instrument [Line Items]
Fixed interest rate								6.04%
Debt Instrument, Collateral Amount								$ 25,034,000
Fixed rate mortgage loans								24,432,000	25,102,000
Mortgages [Member] | Second Wayne, NJ Mortgage [Member] | Construction in Progress [Member]
Debt Instrument [Line Items]
Debt Instrument, Collateral Amount								200,000
Mortgages [Member] | Patchogue NY [Member]
Debt Instrument [Line Items]
Fixed rate mortgage loans												$ 29,100,000
Mortgages [Member] | Hackensack, NJ [Member]
Debt Instrument [Line Items]
Debt Instrument, Collateral Amount								37,619,000
Fixed rate mortgage loans								$ 48,000,000	29,198,000
Mortgages [Member] | Hackensack, NJ [Member] | Pierre Towers, LLC [Member]
Debt Instrument [Line Items]
Fixed interest rate								5.38%
Debt Instrument, Periodic Payment								$ 155,200
Debt Instrument, Collateral Amount								225,851
Loan amount								48,000,000
Amount drawn on loan								$ 960,000
Maturity date of loan								Jan. 01, 2028
Term of the loan								5 years
Net proceeds from refinancing of debt								$ 17,200,000
Mortgage prepayment penalty								$ 1,200,000
Mortgages [Member] | S And A Commercial Associates Limited Partnership [Member]
Debt Instrument [Line Items]
Membership interest percentage								65.00%
Repurchase amount of acquisition loan								$ 11,200,000
Mortgages [Member] | Damascus, MD [Member]
Debt Instrument [Line Items]
Basis points, interest rate								2.10%
Fixed interest rate								3.81%
Debt Instrument, Collateral Amount								$ 26,774,000
Amount drawn on loan								$ 20,000,000
Maturity date of loan								Jan. 03, 2023
Line of credit, remaining capacity								$ 1,850,000
Fixed rate mortgage loans								19,865,000	20,357,000
Mortgages [Member] | Provident Bank Mortgage [Member]
Debt Instrument [Line Items]
Loan amount																$ 16,200,000
Mortgages [Member] | Middletown, NY Mortgage [Member]
Debt Instrument [Line Items]
Fixed rate mortgage loans								$ 15,922,000	16,200,000
Mortgages [Member] | Frederick, MD [Member]
Debt Instrument [Line Items]
Fixed interest rate								5.55%
Debt Instrument, Periodic Payment								$ 45,250
Debt Instrument, Collateral Amount								14,195,000
Monthly principal payment amount								$ 43,250
Mortgages [Member] | Grande Rotunda LLC [Member] | Minimum [Member]
Debt Instrument [Line Items]
Replenish account balance														$ 500,000
Mortgages [Member] | Grande Rotunda LLC [Member] | Maximum [Member]
Debt Instrument [Line Items]
Replenish account balance														$ 1,000,000
Provident Bank [Member]
Debt Instrument [Line Items]
Basis points, interest rate		1.80%						2.75%
Fixed interest rate		4.35%						3.75%
Debt Instrument, Collateral Amount									3,100,000
Loan amount		$ 12,350,000						$ 16,200,000
Amount drawn on loan									3,121,000
Maturity date of loan		Dec. 15, 2027						Oct. 27, 2020
Term of the loan								3 years
Line of credit, maximum borrowing capacity								$ 13,000,000
Line of credit, current borrowing capacity								12,800,000
Line of credit, renewal								$ 100,000
Line of credit				$ 3,100,000
Provident Bank [Member] | Middletown, NY Mortgage [Member]
Debt Instrument [Line Items]
Basis points, interest rate								1.25%
Fixed interest rate								3.75%
Debt Instrument, Collateral Amount								$ 19,231,000
Maturity date of loan								Dec. 15, 2024
Monthly principal payment amount								$ 27,807
People's United Bank [Member]
Debt Instrument [Line Items]
Fixed interest rate															3.53%
Loan amount						$ 25,800,000		19,900,000
Amount drawn on loan															$ 2,320,000
People's United Bank [Member] | Readily Available [Member]
Debt Instrument [Line Items]
Amount drawn on loan															$ 470,000
Manufacturer's and Traders Trust Company [Member] | Wells Fargo Bank [Member]
Debt Instrument [Line Items]
Loan amount					$ 23,500,000
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Amount drawn on loan								141,230,000	141,678,000
Notes Payable, Other Payables [Member] | Frederick, MD [Member]
Debt Instrument [Line Items]
Amount drawn on loan								22,710,000	23,241,000
Notes Payable, Other Payables [Member] | Baltimore, MD [Member]
Debt Instrument [Line Items]
Basis points, interest rate							2.25%
Debt Instrument, Collateral Amount							$ 19,500,000
Loan amount							$ 22,500,000
Amount drawn on loan								118,520,000	$ 115,316,000				$ 2,100,000
Notes Payable, Other Payables [Member] | Baltimore, MD [Member] | Minimum [Member]
Debt Instrument [Line Items]
Amount drawn on loan								116,100,000
Notes Payable, Other Payables [Member] | Baltimore, MD [Member] | Maximum [Member]
Debt Instrument [Line Items]
Amount drawn on loan								$ 120,000,000
Grande Rotunda LLC Construction Loan [Member]
Debt Instrument [Line Items]
Fixed interest rate								3.00%
Loan amount								$ 121,900,000
Maturity date of loan								Mar. 05, 2020
Rotunda [Member]
Debt Instrument [Line Items]
Fixed interest rate								5.13%
Debt Instrument, Collateral Amount								$ 154,526,000
Loan amount								$ 118,500,000

[1] Includes $4,213 that was incurred and accrued in fiscal 2015; paid in fiscal 2016.