Investments in Joint Ventures as of December 31, 2020 (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net	$ 472,317	$ 451,767
Cash and cash equivalents	2,987	21,649
Unrealized rents & receivables	4,342	1,102
Deferred costs	898	4,038
Total Assets	678,190	536,360	$ 538,148
Secured notes payable	222,635	180,890
Other liabilities	28,253	34,126
Capital - Third Parties	396,423	367,654
Total Liabilities and Capital	678,190	536,360
Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets	480,544	478,556
Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP	139,981	174,792
Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital - Third Parties	89,675	88,748
Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital	480,544	478,556
Brooksville Quarry L L C [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net	14,281	14,287
Cash and cash equivalents	18	55
Unrealized rents & receivables	0	0
Deferred costs	2	5
Secured notes payable	0	0
Other liabilities	0	28
Brooksville Quarry L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets	14,301	14,347
Brooksville Quarry L L C [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP	7,488	7,499
Brooksville Quarry L L C [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital - Third Parties	6,813	6,820
Brooksville Quarry L L C [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital	14,301	14,347
B C F R P Realty L L C [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net	21,561	22,067
Cash and cash equivalents	312	90
Unrealized rents & receivables	368	254
Deferred costs	229	336
Secured notes payable	11,384	12,370
Other liabilities	140	123
B C F R P Realty L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets	22,470	22,747
B C F R P Realty L L C [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP	5,473	5,127
B C F R P Realty L L C [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital - Third Parties	5,473	5,127
B C F R P Realty L L C [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital	22,470	22,747
Hyde Park [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		591
Cash and cash equivalents		0
Unrealized rents & receivables		0
Deferred costs		0
Secured notes payable		0
Other liabilities		0
Hyde Park [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets		591
Hyde Park [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		591
Hyde Park [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital - Third Parties		0
Hyde Park [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital		591
Amber Ridge Loan [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net	11,466	10,026
Cash and cash equivalents	0	0
Unrealized rents & receivables	0	0
Deferred costs	0	0
Secured notes payable	0	0
Other liabilities	0	0
Amber Ridge Loan [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets	11,466	10,026
Amber Ridge Loan [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP	11,466	10,026
Amber Ridge Loan [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital - Third Parties	0	0
Amber Ridge Loan [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital	11,466	10,026
Apartment Mixed Use [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net	424,495	404,796
Cash and cash equivalents	2,657	21,504
Unrealized rents & receivables	3,974	848
Deferred costs	667	3,697
Secured notes payable	211,251	168,520
Other liabilities	28,113	33,975
Apartment Mixed Use [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets	431,793	430,845
Apartment Mixed Use [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP	115,040	151,549
Apartment Mixed Use [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital - Third Parties	77,389	76,801
Apartment Mixed Use [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital	$ 431,793	$ 430,845