Investments in unconsolidated joint ventures (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Total investments	$ 145,443,000	$ 167,071,000
Total assets of the partnership	678,190,000	536,360,000	$ 538,148,000
Partnership profit (loss)	40,094,000	11,722,000	15,678,000
Share of profit (loss) of the partnership	(5,754,000)	(5,690,000)	$ (1,954,000)
Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	480,544,000	478,556,000
Partnership profit (loss)	(8,573,000)	(5,925,000)
Real Estate Partnership Net Income Loss [Member]
Schedule of Equity Method Investments [Line Items]
Share of profit (loss) of the partnership	$ (5,754,000)	$ (5,690,000)
Brooksville Quarry L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%	50.00%
Total investments	$ 7,488,000	$ 7,499,000
Partnership profit (loss)	(82,000)	(78,000)
Share of profit (loss) of the partnership	(41,000)	(39,000)
Brooksville Quarry L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 14,301,000	$ 14,347,000
B C F R P Realty L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%	50.00%
Total investments	$ 5,530,000	$ 5,184,000
Partnership profit (loss)	(230,000)	(411,000)
Share of profit (loss) of the partnership	(115,000)	(207,000)
B C F R P Realty L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	22,470,000	$ 22,747,000
Riverfront Holdings I I L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage		80.00%
Total investments	0	$ 23,533,000
Partnership profit (loss)	(760,000)	(4,573,000)
Share of profit (loss) of the partnership	(628,000)	(3,907,000)
Riverfront Holdings I I L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 0	$ 108,538,000
Bryant Street Partnerships [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	61.36%	61.36%
Total investments	$ 59,558,000	$ 60,159,000
Partnership profit (loss)	(6,084,000)	(836,000)
Share of profit (loss) of the partnership	(4,954,000)	(2,130,000)
[custom:InterestIncomePreferred]	747,000	1,146,000
[custom:GuaranteeLiabilityAmortization]	471,000	471,000
Bryant Street Partnerships [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	204,082,000	$ 173,814,000
Aberdeen Station [Member]
Schedule of Equity Method Investments [Line Items]
Total investments	514,000
Partnership profit (loss)	0
Share of profit (loss) of the partnership	0
Aberdeen Station [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 514,000
D S T Hickory Creek [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	26.65%	26.65%
Total investments	$ 6,000,000	$ 6,000,000
Partnership profit (loss)	(481,000)	(367,000)
Share of profit (loss) of the partnership	343,000	339,000
D S T Hickory Creek [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	46,048,000	47,761,000
Amber Ridge Loan [Member]
Schedule of Equity Method Investments [Line Items]
Total investments	11,466,000	10,026,000
Partnership profit (loss)	0	0
Share of profit (loss) of the partnership		0
Amber Ridge Loan [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 11,466,000	$ 10,026,000
Half St Owner L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	61.37%	61.37%
Total investments	$ 38,693,000	$ 37,875,000
Partnership profit (loss)	12,000	158,000
Share of profit (loss) of the partnership	20,000	164,000
Half St Owner L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 93,932,000	$ 54,275,000
Greenville Woodfield Partnerships [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	40.00%	40.00%
Total investments	$ 16,194,000	$ 16,204,000
Partnership profit (loss)	(948,000)	182,000
Share of profit (loss) of the partnership	(379,000)	90,000
Greenville Woodfield Partnerships [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 87,731,000	46,457,000
Hyde Park [Member]
Schedule of Equity Method Investments [Line Items]
Total investments		591,000
Partnership profit (loss)		0
Share of profit (loss) of the partnership		0
Hyde Park [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership		$ 591,000