Amount of non-cash amortization of intangible asset (liability) for above and below market leases.

No definition available.

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

- Definition

Amount of amortization of acquired leases acquired as part of a real property acquisition at below market lease rate with a finite life.

+ References

No definition available.

+ Details

Name:	us-gaap_AmortizationOfBelowMarketLease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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

- Definition

Amount before amortization of leases acquired as part of a real property acquisition at below market lease rate with a finite life.

+ References

No definition available.

+ Details

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

- Definition

This element represents the amount of value allocated by a lessor (acquirer) to lease agreements which exist at acquisition of a leased property. Such amount may include the value assigned to existing tenant relationships and excludes the market adjustment component of the value assigned for above or below-market leases acquired.

+ References

No definition available.

+ Details

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

- Definition

This element represents the identifiable intangible asset established upon acquisition based on a favorable difference between the terms of an acquired lease and the current market terms for that lease at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.15)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_StatementScenarioAxis=FRPH_TransitScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=FRPH_TransitBusinessParkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Real Estate Business Park Acquisitions - Intangible asset amortization Transit Business Park (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Jun. 20, 2013
Below market leases initial values						$ 220	$ 220
Transit Forecasted amortization
In-place Leases	$ 17	$ 43	$ 43	$ 43	$ 44
Above Market Leases	$ 3	$ 4	$ 4	$ 4	$ 4
Transit Business Park
In-place leases initial value									$ 806
Above market leases initial value									48
Below market leases initial values									$ 156
In-place Leases						44	63	$ 369
Above Market Leases						4	4	12
Below Market Leases						$ 9	$ 37	$ 86