Additional service expenses.

No definition available.

Name:	frevsob_AdditionalServices
Namespace Prefix:	frevsob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Asset management fees percentage rate.

+ References

No definition available.

+ Details

Name:	frevsob_AssetManagementFeesPercentageRate
Namespace Prefix:	frevsob_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate costs related to management of owned properties during the reporting period.

+ References

No definition available.

+ Details

Name:	frevsob_CostsForOwnedPropertyManagement
Namespace Prefix:	frevsob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The expense incurred to persons or entities for securing insurance coverage for properties and subsidiaries.

+ References

No definition available.

+ Details

Name:	frevsob_InsuranceCommissionsPaid
Namespace Prefix:	frevsob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of commissions expense incurred because the lessor of real estate obtained a lessee for a rental property through a real estate agent and generally recurring costs associated with operations.

+ References

No definition available.

+ Details

Name:	frevsob_LeasingCommissionsAndReimbursementOfOperatingExpenses
Namespace Prefix:	frevsob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Loan commission.

+ References

No definition available.

+ Details

Name:	frevsob_LoanCommission
Namespace Prefix:	frevsob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pro-rata share based funding amount.

+ References

No definition available.

+ Details

Name:	frevsob_ProrataShareBasedFundingAmount
Namespace Prefix:	frevsob_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Repayment to affiliate.

+ References

No definition available.

+ Details

Name:	frevsob_RepaymentToAffiliate
Namespace Prefix:	frevsob_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(5))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.15(a))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

+ Details

Name:	us-gaap_AccruedLiabilitiesCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of debt and lease obligation, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(21))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the total principal payments made during the annual reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentAnnualPrincipalPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of payable due to an entity that is affiliated with the reporting entity by means of direct or indirect ownership. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a)(5))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(12)(b)(3))
-URI https://asc.fasb.org/extlink&oid=120401414&loc=d3e603758-122996

+ Details

Name:	us-gaap_DueToAffiliateCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of commissions expense incurred because the lessor of real estate obtained a lessee for a rental property through a real estate agent.

+ References

No definition available.

+ Details

Name:	us-gaap_LeasingCommissionsExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(c))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateCommercialAndConsumerNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fees charged annually for the professional services of a trustee, usually quoted as a percentage of the funds being managed. The fee for appointing an offshore Trustee is included in the trust price.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

+ Details

Name:	us-gaap_TrusteeFees
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=frevsob_Rotunda100MembersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_Subsidiaries7Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_Subsidiaries8Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_RotundaPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_DamascusPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_WestridgeSquarePropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_BouldersPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_Subsidiaries9Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=frevsob_Subsidiaries10Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_DirectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_ImmediateFamilyMemberOfManagementOrPrincipalOwnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=frevsob_Director2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=frevsob_DavidHekemianMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Management agreement, fees and transactions with related party (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2022	Apr. 30, 2021	Oct. 31, 2021	May 31, 2022	Mar. 10, 2022	Dec. 30, 2021
Related Party Transaction [Line Items]
Asset management fees	$ 314,000	$ 561,000	$ 811,000	$ 1,087,000
Insurance commissions	0	0	0	10,000
Secured loans receivable	222,000		222,000		$ 5,292,000
Letter of Credit [Member]
Related Party Transaction [Line Items]
Sales commissions				32,500
Rotunda 100 members [Member]
Related Party Transaction [Line Items]
Secured loans receivable	5,100,000		5,100,000
Principal amount on notes paid off	167,000		167,000		4,000,000
Unpaid accrued interest	$ 56,000		$ 56,000		1,292,000
Grande Rotunda, LLC [Member]
Related Party Transaction [Line Items]
Ownership by noncontrolling owners (percentage)	40.00%		40.00%
Ownership by parent (percentage)	50.00%		50.00%
Due to affiliate					3,300,000			$ 3,300,000
Principal amount on notes paid off					7,000,000			$ 31,000,000
Loan commission				150,000
Repayment to affiliate					$ 2,800,000
FREIT [Member]
Related Party Transaction [Line Items]
Ownership by noncontrolling owners (percentage)	40.00%		40.00%
Loan commission				54,000
Promissory note							$ 400,000
FREIT [Member] \| Subsequent Event [Member]
Related Party Transaction [Line Items]
Pro-rata share based funding amount						$ 200,000
Rotunda Property [Member]
Related Party Transaction [Line Items]
Loan commission			$ 4,777,000
Damascus Property [Member]
Related Party Transaction [Line Items]
Loan commission			917,000
Westridge Square Property [Member]
Related Party Transaction [Line Items]
Loan commission			525,000
Boulders Property [Member]
Related Party Transaction [Line Items]
Loan commission			$ 75,000
H-TPKE [Member]
Related Party Transaction [Line Items]
Ownership by noncontrolling owners (percentage)	60.00%		60.00%
Ownership by parent (percentage)	73.00%		73.00%
Promissory note							$ 600,000
H-TPKE [Member] \| Subsequent Event [Member]
Related Party Transaction [Line Items]
Pro-rata share based funding amount						300,000
Wayne PSC [Member] \| Subsequent Event [Member]
Related Party Transaction [Line Items]
Pro-rata share based funding amount						$ 500,000
Managing Agent Hekemian & Co [Member]
Related Party Transaction [Line Items]
Asset management fees	$ 306,000	549,000	$ 790,000	1,062,000
Leasing commissions and reimbursement of operating expenses	164,000	126,000	348,000	255,000
Insurance commissions	7,000	2,000	59,000	71,000
Additional services	0	236,500	6,294,000	236,500
Robert S. Hekemian, Jr. [Member]
Related Party Transaction [Line Items]
Trustee fees and related interest payable in stock units	141,000	116,000	279,000	232,000
Allan Tubin [Member]
Related Party Transaction [Line Items]
Trustee fees and related interest payable in stock units	10,000	8,000	20,000	15,000
David Hekemian [Member]
Related Party Transaction [Line Items]
Trustee fees and related interest payable in stock units	$ 14,000	$ 10,000	$ 29,000	$ 27,000
Minimum [Member]
Related Party Transaction [Line Items]
Asset management fees percentage rate			4.00%
Maximum [Member]
Related Party Transaction [Line Items]
Asset management fees percentage rate			5.00%