Investments in Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jul. 31, 2019	Dec. 24, 2018	May 04, 2018	Apr. 26, 2016	Oct. 04, 2006
Total Investment	$ 159,779		$ 159,779		$ 160,452
Total Assets of the Partnership	408,448		408,448		334,742
Profit (Loss) of the Partnership			(1,456)		(1,201)
Company's share of Net Loss of the Partnership	(1,343)	$ (272)	(1,985)	$ (536)	(1,954)
Investments in real estate, net	369,962		369,962		287,106
Cash and cash equivalents	33,587		33,587		45,909
Deferred costs	3,874		3,874		821
Unrealized rents & receivable	1,025		1,025		906
Secured notes payable	137,420		137,420		81,573
Other liabilities	25,421		25,421		27,524
Capital - FRP	168,589		168,589		170,832
Capital - Third parties	77,018		77,018		54,813
Total liabilities and capital	$ 408,448		$ 408,448		$ 334,742
Brooksville Quarry, LLC
Ownership percent	50.00%		50.00%		50.00%					50.00%
Total Investment	$ 7,476		$ 7,476		$ 7,499
Total Assets of the Partnership	14,310		14,310		14,316
Profit (Loss) of the Partnership			(42)		(84)
Company's share of Net Loss of the Partnership			(21)		(42)
Investments in real estate, net	14,290		14,290		14,293
Cash and cash equivalents	18		18		18
Deferred costs	2		2		5
Unrealized rents & receivable	0		0		0
Secured notes payable	0		0		0
Other liabilities	41		41		2
Capital - FRP	7,476		7,476		7,500
Capital - Third parties	6,793		6,793		6,814
Total liabilities and capital	$ 14,310		$ 14,310		$ 14,316
BC FRP Realty, LLC
Ownership percent	50.00%		50.00%		50.00%				50.00%
Total Investment	$ 5,286		$ 5,286		$ 5,391
Total Assets of the Partnership	22,689		22,689		22,969
Profit (Loss) of the Partnership			(210)		(1,114)
Company's share of Net Loss of the Partnership			(104)		(591)
Investments in real estate, net	22,187		22,187		22,423
Cash and cash equivalents	59		59		15
Deferred costs	213		213		311
Unrealized rents & receivable	230		230		220
Secured notes payable	12,130		12,130		12,103
Other liabilities	105		105		196
Capital - FRP	5,227		5,227		5,335
Capital - Third parties	5,227		5,227		5,335
Total liabilities and capital	$ 22,689		$ 22,689		$ 22,969
RiverFront Holdings II, LLC
Ownership percent	80.00%		80.00%		80.00%			80.00%
Total Investment	$ 25,484		$ 25,484		$ 25,975
Total Assets of the Partnership	104,426		104,426		88,235
Profit (Loss) of the Partnership			(1,326)		(95)
Company's share of Net Loss of the Partnership			(1,409)		(871)
Investments in real estate, net	103,602		103,602		87,521
Cash and cash equivalents	720		720		630
Deferred costs	26		26		2
Unrealized rents & receivable	78		78		82
Secured notes payable	60,252		60,252		38,564
Other liabilities	2,094		2,094		6,771
Capital - FRP	36,732		36,732		37,284
Capital - Third parties	5,348		5,348		5,616
Total liabilities and capital	$ 104,426		$ 104,426		$ 88,235
Bryant Street Partnerships
Ownership percent	61.36%		61.36%		61.36%		61.36%
Total Investment	$ 59,549		$ 59,549		$ 58,353
Total Assets of the Partnership	133,553		133,553		96,477
Profit (Loss) of the Partnership			0		260
Company's share of Net Loss of the Partnership			(825)		(573)
Investments in real estate, net	132,932		132,932		95,903
Cash and cash equivalents	512		512		387
Deferred costs	14		14		29
Unrealized rents & receivable	95		95		158
Secured notes payable	35,770		35,770		1,660
Other liabilities	19,405		19,405		17,183
Capital - FRP	58,224		58,224		57,479
Capital - Third parties	20,154		20,154		20,155
Total liabilities and capital	133,553		133,553		96,477
Hyde Park
Total Investment	1,214		1,214		3,492
Total Assets of the Partnership	1,214		1,214		3,492
Profit (Loss) of the Partnership			0		0
Company's share of Net Loss of the Partnership			0		0
Investments in real estate, net	1,214		1,214		3,492
Cash and cash equivalents	0		0		0
Deferred costs	0		0		0
Unrealized rents & receivable	0		0		0
Secured notes payable	0		0		0
Other liabilities	0		0		0
Capital - FRP	1,214		1,214		3,492
Capital - Third parties	0		0		0
Total liabilities and capital	$ 1,214		$ 1,214		$ 3,492
DST Hickory Creek
Ownership percent	26.65%		26.65%		26.65%	26.65%
Total Investment	$ 6,000		$ 6,000		$ 6,000
Total Assets of the Partnership	48,651		48,651		49,369
Profit (Loss) of the Partnership			(162)		(168)
Company's share of Net Loss of the Partnership			168		123
Investments in real estate, net	46,106		46,106		46,685
Cash and cash equivalents	1,483		1,483		1,764
Deferred costs	440		440		474
Unrealized rents & receivable	622		622		446
Secured notes payable	29,268		29,268		29,246
Other liabilities	171		171		120
Capital - FRP	5,120		5,120		6,000
Capital - Third parties	14,092		14,092		14,003
Total liabilities and capital	48,651		48,651		49,369
Amber Ridge
Total Investment	1,183		1,183		509
Total Assets of the Partnership	1,183		1,183		509
Profit (Loss) of the Partnership			0		0
Company's share of Net Loss of the Partnership			0		0
Investments in real estate, net	1,183		1,183		509
Cash and cash equivalents	0		0		0
Deferred costs	0		0		0
Unrealized rents & receivable	0		0		0
Secured notes payable	0		0		0
Other liabilities	0		0		0
Capital - FRP	1,183		1,183		509
Capital - Third parties	0		0		0
Total liabilities and capital	$ 1,183		$ 1,183		$ 509
1800 Half Street
Ownership percent	61.37%		61.37%		59.73%
Total Investment	$ 37,537		$ 37,537		$ 37,314
Total Assets of the Partnership	39,327		39,327		40,161
Profit (Loss) of the Partnership			126		0
Company's share of Net Loss of the Partnership			126		0
Investments in real estate, net	27,603		27,603		14,391
Cash and cash equivalents	8,917		8,917		25,770
Deferred costs	2,807		2,807		0
Unrealized rents & receivable	0		0		0
Secured notes payable	0		0		0
Other liabilities	392		392		1,363
Capital - FRP	37,460		37,460		37,314
Capital - Third parties	1,475		1,475		1,484
Total liabilities and capital	$ 39,327		$ 39,327		$ 40,161
Woodfield Partnerships
Ownership percent	40.00%		40.00%		40.00%
Total Investment	$ 16,050		$ 16,050		$ 15,919
Total Assets of the Partnership	43,095		43,095		19,214
Profit (Loss) of the Partnership			158		0
Company's share of Net Loss of the Partnership			80		0
Investments in real estate, net	20,845		20,845		1,889
Cash and cash equivalents	21,878		21,878		17,325
Deferred costs	372		372		0
Unrealized rents & receivable	0		0		0
Secured notes payable	0		0		0
Other liabilities	3,213		3,213		1,889
Capital - FRP	15,953		15,953		15,919
Capital - Third parties	23,929		23,929		1,406
Total liabilities and capital	43,095		43,095		19,214
Apartment Mixed Use Totals
Total Assets of the Partnership	369,052		369,052		293,456
Investments in real estate, net	331,088		331,088		246,389
Cash and cash equivalents	33,510		33,510		45,876
Deferred costs	3,659		3,659		505
Unrealized rents & receivable	795		795		686
Secured notes payable	125,290		125,290		69,470
Other liabilities	25,275		25,275		27,326
Capital - FRP	153,489		153,489		153,996
Capital - Third parties	64,998		64,998		42,664
Total liabilities and capital	$ 369,052		$ 369,052		$ 293,456