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Mortgages payable and credit line (Narrative) (Details) - USD ($)							1 Months Ended						2 Months Ended	12 Months Ended
	Aug. 26, 2019	Apr. 03, 2019	Feb. 28, 2018	Feb. 07, 2018	Dec. 07, 2017	Jan. 14, 2013	Feb. 28, 2018	Dec. 31, 2017	Apr. 28, 2017	Sep. 29, 2016	Jun. 30, 2016	Feb. 01, 2010	Feb. 28, 2018	Oct. 31, 2019	Jan. 21, 2019	Oct. 31, 2018	Jan. 08, 2018	Nov. 23, 2016
Debt Instrument [Line Items]
Amount drawn on loan														$ 352,790,000		$ 350,504,000
Line of Credit [Member]
Debt Instrument [Line Items]
Maturity date of loan														Oct. 27, 2020
Line of Credit, available														$ 13,000,000
Line of Credit repaid			$ 3,100,000
Grande Rotunda LLC [Member]
Debt Instrument [Line Items]
Fee amount							$ 900,000
Station Place on Monmouth, LLC [Member]
Debt Instrument [Line Items]
Basis points, interest rate					1.80%
Fixed interest rate current loan					4.35%
Loan amount					$ 12,350,000
Maturity date of loan					Dec. 15, 2027
Term of the loan					10 years
Percentage of acquisition					100.00%
Portion of outstanding principal balance guaranteed by FREIT															$ 2,350,000
WestFREIT Corp [Member]
Debt Instrument [Line Items]
Refinanced loan amount									$ 22,000,000
Basis points, interest rate									2.75%
Loan amount									$ 23,500,000
Maturity date of loan									Apr. 28, 2019
Net proceeds from refinancing of debt									$ 1,100,000
Percentage of acquisition									100.00%
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]
Basis points, interest rate												2.25%
Debt Instrument, collateral amount												$ 19,500,000
Loan amount												$ 22,500,000						$ 114,000,000
Interest reserve to Wells Fargo																		$ 2,000,000
Accrued interest on development fee paid				$ 45,000
Amount repaid				$ 115,300,000
Wells Fargo Bank [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Basis points, interest rate								2.85%			2.50%		3.15%
Replenish account balance											$ 1,000,000
Wells Fargo Bank [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Basis points, interest rate								0.35%			0.25%		0.65%
Replenish account balance											$ 500,000
Mortgages [Member]
Debt Instrument [Line Items]
Fixed rate mortgage loans														212,070,000		209,274,000
Variable rate mortgage loan														$ 140,720,000		141,230,000
Mortgages [Member] \| Rockaway, NJ Mortgage [Member]
Debt Instrument [Line Items]
Fixed interest rate current loan														5.37%
Debt Instrument, Periodic Payment														$ 115,850
Debt Instrument, collateral amount														15,276,000
Fixed rate mortgage loans														$ 15,615,000		16,152,000
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 current loan														4.75%
Debt Instrument, Periodic Payment														$ 129,702
Debt Instrument, collateral amount														7,121,000
Loan amount														22,750,000
Fixed rate mortgage loans														$ 18,973,000		19,611,000
Mortgages [Member] \| Patchogue, NY [Member]
Debt Instrument [Line Items]
Fixed interest rate current loan														4.50%
Debt Instrument, Periodic Payment														$ 19,600
Loan amount														5,200,000
Fixed rate mortgage loans																5,231,000
Mortgages [Member] \| Wayne, NJ Mortgage [Member] \| Berdan Court, LLC [Member]
Debt Instrument [Line Items]
Refinanced loan amount	$ 17,000,000
Fixed interest rate on old loan	6.09%
Fixed interest rate current loan	3.54%
Debt Instrument, Periodic Payment	$ 85,004
Debt Instrument, collateral amount														1,622,000
Loan amount	$ 28,815,000
Maturity date of loan	Sep. 01, 2029
Term of the loan	10 years
Net proceeds from refinancing of debt	$ 11,600,000
Future periodic payment including principal	$ 130,036
Percentage of acquisition	100.00%
Fixed rate mortgage loans														$ 28,815,000		17,334,000
Mortgages [Member] \| Hackensack, NJ [Member] \| Pierre Towers, LLC [Member]
Debt Instrument [Line Items]
Fixed interest rate on old loan														5.38%
Debt Instrument, Periodic Payment														$ 155,200
Debt Instrument, collateral amount														36,661,000
Loan amount														48,000,000
Loan deposit refunded														$ 960,000
Maturity date of loan														Jan. 01, 2028
Term of the loan														10 years
Net proceeds from refinancing of debt														$ 17,200,000
Future periodic payment including principal														225,851
Mortgage prepayment penalty														1,200,000
Fixed rate mortgage loans														$ 48,000,000		48,000,000	$ 29,100,000
Mortgages [Member] \| River Edge, NJ Refinanced Mortgage [Member]
Debt Instrument [Line Items]
Fixed interest rate current loan														4.54%
Debt Instrument, Periodic Payment														$ 57,456
Debt Instrument, collateral amount														755,000
Loan amount														11,200,000
Mortgages [Member] \| Red Bank, NJ Refinanced Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, collateral amount														$ 19,035,000
Mortgages [Member] \| Westwood, NJ #3 [Member]
Debt Instrument [Line Items]
Fixed interest rate current loan														4.62%
Debt Instrument, Periodic Payment														$ 120,752
Debt Instrument, collateral amount														8,934,000
Fixed rate mortgage loans														19,617,000		20,134,000
Mortgages [Member] \| Wayne, PSC LLC [Member]
Debt Instrument [Line Items]
Refinanced loan amount										$ 24,200,000				$ 25,800,000
Basis points, interest rate														2.20%
Fixed interest rate on old loan														6.04%
Fixed interest rate current loan														3.625%
Membership interest percentage														40.00%
Debt Instrument, collateral amount														$ 24,787,000
Debt Instrument, collateral amount classified as construction in progress														400,000
Loan amount														$ 25,800,000
Description of variable interest rate														a reduction in interest rate from 6.04% to 3.625%
Maturity date of loan														Oct. 01, 2026
Net proceeds from refinancing of debt														$ 1,000,000
Fixed rate mortgage loans														$ 23,737,000		24,432,000
Mortgages [Member] \| S And A Commercial Associates Limited Partnership [Member]
Debt Instrument [Line Items]
Membership interest percentage														65.00%
Net proceeds from refinancing of debt														$ 11,200,000
Mortgages [Member] \| Damascus, MD [Member]
Debt Instrument [Line Items]
Basis points, interest rate														2.10%
Fixed interest rate tranche one														3.81%
Fixed interest rate tranche two														3.53%
Debt Instrument, collateral amount														$ 26,136,000
Maturity date of loan														Jan. 03, 2023
Escrow released														$ 1,850,000
Fixed rate mortgage loans														19,354,000		19,865,000
Mortgages [Member] \| Middletown, NY Mortgage [Member]
Debt Instrument [Line Items]
Fixed rate mortgage loans														15,588,000		$ 15,922,000
Mortgages [Member] \| Frederick, MD [Member]
Debt Instrument [Line Items]
Debt Instrument, collateral amount														$ 13,398,000
Provident Bank [Member] \| Middletown, NY Mortgage [Member]
Debt Instrument [Line Items]
Basis points, interest rate														1.25%
Fixed interest rate current loan														3.75%
Debt Instrument, collateral amount														$ 18,735,000
Loan amount														$ 16,200,000
Maturity date of loan														Dec. 15, 2024
Monthly principal payment amount														$ 27,807
WestFREIT Corp [Member]
Debt Instrument [Line Items]
Basis points, interest rate		2.40%
Debt Instrument, Periodic Payment		$ 47,250
Loan amount		$ 22,500,000
Maturity date of loan		May 01, 2020
Rotunda [Member]
Debt Instrument [Line Items]
Basis points, interest rate														2.85%
Variable interest rate														4.84%
Debt Instrument, collateral amount														$ 151,130,000
Loan amount														$ 118,500,000
Maturity date of loan														Feb. 06, 2021
Grande Rotunda LLC Construction Loan [Member]
Debt Instrument [Line Items]
Interest rate cap														3.00%
Loan amount														$ 121,900,000
Line of Credit, available														$ 3,380,000