Investments in Joint Ventures (Details Narrative) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended			12 Months Ended
	May 31, 2016 USD ($)	Sep. 30, 2019 USD ($) integer	Sep. 30, 2018 USD ($)	Dec. 31, 2006 USD ($)	Sep. 30, 2019 USD ($) integer	Sep. 30, 2018 USD ($)	Sep. 30, 2016 USD ($) a ft²	Dec. 31, 2018 USD ($) integer	Dec. 31, 2017	Jul. 31, 2019 USD ($) a ft² integer	Jun. 26, 2019 USD ($) integer	Mar. 13, 2019 USD ($)	Dec. 24, 2018 a	May 04, 2018 USD ($)	Jan. 27, 2018 USD ($)	Sep. 28, 2017 USD ($) integer	Oct. 04, 2006 a
Company's share of the loss of the joint venture		$ 746	$ 13		$ 1,282	$ 36		$ 88
Joint Venture consolidated retained earnings		(3,637)			(3,637)			$ (2,702)
Cash contribution					16,226	$ 7,160
Difference between capital recorded by the Company and the joint ventures		10,345			10,345
Bryant Street and MRP
Loan guarantee amount		$ 26,000			$ 26,000
Loan guarantee term					48 months
Loan guarantee description					The Company and MRP guaranteed $26 million of the loan in exchange for a 1% lower interest rate. The Company and MRP have a side agreement limiting the Company’s guarantee to its proportionate ownership. The value of the guarantee was calculated at $1.9 million based on the present value of the 1% interest savings over the anticipated 48 month term. This amount is included as part of the Company’s investment basis and is amortized to expense over the 48 months. The Company will evaluate the guarantee liability based upon the success of the project and assuming no payments are made under the guarantee the Company will have a gain for $1.9 million when the loan is paid in full.
Loan guarantee interest savings		1.00%			1.00%
Loan guarantee present value		$ 1,900			$ 1,900
BC FRP Realty, LLC Debt
Construction financing through September 15, 2022																$ 17,250
Interest rate over LIBOR									2.50%
Outstanding balance		11,538			11,538
Buildings | integer																4
Eagle BankRiverFront Holdings II, LLC
Interest rate over LIBOR								3.25%
Outstanding balance		27,671			$ 27,671
Loan commitment														$ 71,000
Loan description								The loan is interest only and matures in 36 months with a 12 month extension assuming completion of construction and at least one occupancy. There is a provision for an additional 60 months extension with a 30 year amortization of principal at 2.15% over 7 year US Treasury Constant if NOI is sufficient for a 9% yield.
Bryant Street Partnerships Construction Loan
Interest rate over LIBOR					2.25%
Outstanding balance		$ 0			$ 0
Loan commitment												$ 132,000
Loan description					The loan matures March 13, 2023 with up to two extension of one year each upon certain conditions.
Bryant Street Partnerships Construction Loan Extension 1
Debt service coverage												1.1
Loan-to-value												65.00%
Bryant Street Partnerships Construction Loan Extension 2
Debt service coverage												1.25
Loan-to-value												65.00%
Vulcan
Joint venture percentage stake																	50.00%
Acres conributed | a																	553
Vulcan leasehold interest | a																	3,443
FRP additional contribution for land				$ 3,018
Additional land acquired | a																	288
St Johns Properties JV St Johns
Value of land contributed							$ 3,240
Joint venture percentage stake							50.00%
Acres conributed | a							10
MRP
Other ownership capital contribution								$ 5,600
Development fee								$ 725
DST CS1031 Hickory Creek
Square feet | ft²										273,940
Land acreage | a										20.4
Buildings | integer										19
Interest rate										3.74%
Financing term		10 years
Amortization period		30 years
Financing obtained										$ 29,672
Interest only period		5 years
Property value										$ 45,600
Brooksville Quarry, LLC
Land acreage | a																	4,300
Joint venture percentage stake		50.00%			50.00%			50.00%									50.00%
Acres conributed | a																	3,443
Book value of land contribution				2,548
FRP additional contribution for land				$ 3,018
Additional land acquired | a																	288
Company's share of the loss of the joint venture					$ 34			$ 61
BC FRP Realty, LLC
Square feet | ft²							329,000
Value of land contributed							$ 7,500
Joint venture percentage stake		50.00%			50.00%		50.00%	50.00%
Distribution received	$ 2,130
Acres conributed | a							25
Company's share of the loss of the joint venture					$ 495			$ 0
Hyde Park
Company's share of the loss of the joint venture					0			(39)
Equity method loan balance		$ 1,047			$ 1,047
Loan commitment															$ 3,500
Interest rate															10.00%
Preferred return															20.00%
No. of townhomes | integer		122			122
No. Single family homes | integer		4			4
RiverFront Holdings II, LLC
Value of land contributed								$ 16,300
Joint venture percentage stake		80.00%			80.00%			80.00%
Book value of land contribution								$ 4,600
Company's share of the loss of the joint venture					$ 597			66
Cash contribution								6,200
Preferred equity financing								$ 13,750
Preferred equity financing advanced					$ 13,750
Preferred equity financing interest rate														7.50%
Bryant Street Partnerships
Number of partnerships | integer								4
Land acreage | a													5
Joint venture percentage stake		61.36%			61.36%			61.36%					61.36%
Company's share of the loss of the joint venture					$ 130			$ 0
Cash contribution								32,000
Preferred equity financing								$ 23,000
Preferred equity financing interest rate													8.00%
Amber Ridge
Company's share of the loss of the joint venture					$ 0
Loan commitment											$ 18,500
Interest rate											10.00%
Preferred return											20.00%
No. of townhomes | integer											190
DST Hickory Creek
Joint venture percentage stake		26.65%			26.65%					26.65%
Distribution received		$ 40
Company's share of the loss of the joint venture					$ 26
Cash contribution		$ 6,000