Investments in Apartment/Mixed Use as of June 30, 2021 (Details) - USD ($) $ in Thousands		Jun. 30, 2021		Mar. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		$ 412,178			$ 451,767
Cash and cash equivalents		9,478			21,649
Unrealized rents & receivables		1,612			1,102
Deferred costs		3,448			4,038
Total Assets		681,252			536,360
Secured notes payable		169,372			180,890
Other liabilities		29,646			34,126
Capital – Third Parties		396,561			367,654
Total Liabilities and Capital		681,252			536,360
Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets		426,716			478,556
Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		140,639			174,792
Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital – Third Parties		87,059			88,748
Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital		426,716			478,556
Riverfront Holdings I I L L C [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		0			105,737
Cash and cash equivalents		0			2,626
Unrealized rents & receivables		0			13
Deferred costs		0			162
Total Assets				$ 150,082
Secured notes payable		0			64,982
Other liabilities		0			4,189
Capital - FRP				18,513
Capital – Third Parties				44,200
Total Liabilities and Capital				$ 150,082
Riverfront Holdings I I L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets		0	[1]		108,538
Riverfront Holdings I I L L C [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		0			34,667
Riverfront Holdings I I L L C [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital – Third Parties		0			4,700
Riverfront Holdings I I L L C [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital		0			108,538
Bryant Street Partnerships [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		195,806			173,560
Cash and cash equivalents		579			111
Unrealized rents & receivables		233			58
Deferred costs		28			85
Secured notes payable		103,546			72,471
Other liabilities		16,441			22,952
Bryant Street Partnerships [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets	[1]	196,646			173,814
Bryant Street Partnerships [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		57,759			58,559
Bryant Street Partnerships [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital – Third Parties		18,900			19,832
Bryant Street Partnerships [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital		196,646			173,814
D S T Hickory Creek [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		44,579			45,379
Cash and cash equivalents		1,121			1,202
Unrealized rents & receivables		935			775
Deferred costs		371			405
Secured notes payable		29,314			29,291
Other liabilities		179			107
D S T Hickory Creek [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets		47,006			47,761
D S T Hickory Creek [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		4,667			4,894
D S T Hickory Creek [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital – Third Parties		12,846			13,469
D S T Hickory Creek [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital		47,006			47,761
Half St Owner L L C [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		56,555			37,452
Cash and cash equivalents		7,089			14,011
Unrealized rents & receivables		0			2
Deferred costs		2,810			2,810
Secured notes payable		0			0
Other liabilities		9,827			1,953
Half St Owner L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets		66,454			54,275
Half St Owner L L C [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		37,485			37,466
Half St Owner L L C [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital – Third Parties		19,142			14,856
Half St Owner L L C [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital		66,454			54,275
Greenville Woodfield Partnerships [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		67,337			42,668
Cash and cash equivalents		324			3,554
Unrealized rents & receivables		0			0
Deferred costs		0			235
Secured notes payable		24,748			1,776
Other liabilities		3,005			4,774
Greenville Woodfield Partnerships [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets		67,661			46,457
Greenville Woodfield Partnerships [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		15,963			15,963
Greenville Woodfield Partnerships [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital – Third Parties		23,945			23,944
Greenville Woodfield Partnerships [Member] | Real Estate Partnership Total Liabilities And Capital [Member]
Schedule of Equity Method Investments [Line Items]
Total Liabilities and Capital		67,661			46,457
Apartment Mixed Use [Member]
Schedule of Equity Method Investments [Line Items]
Investments in real estate, net		364,277			404,796
Cash and cash equivalents		9,113			21,504
Unrealized rents & receivables		1,168			848
Deferred costs		3,209			3,697
Secured notes payable		157,608			168,520
Other liabilities		29,452			33,975
Apartment Mixed Use [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total Assets		377,767			430,845
Apartment Mixed Use [Member] | Real Estate Partnership F R P [Member]
Schedule of Equity Method Investments [Line Items]
Capital - FRP		115,874			151,549
Apartment Mixed Use [Member] | Real Estate Partnership Third Parties [Member]
Schedule of Equity Method Investments [Line Items]
Capital – Third Parties		74,833			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		$ 377,767			$ 430,845

[1] Riverfront Holdings II, LLC was consolidated on March 31, 2021. Bryant Street Partnerships includes $471,000 in 2021 and $1,146,000 in 2020 for the Company’s share of preferred interest and $236,000 in 2021 and $471,000 in 2020 for amortization of guarantee liability related to the Bryant Street loan.