Investments in unconsolidated joint ventures (Details) - USD ($)	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	May 04, 2018
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage			70.41%
Total investments	$ 139,655,000			$ 139,655,000		$ 145,443,000
Total assets of the partnership	677,040,000			677,040,000		678,190,000
Partnership profit (loss)	582,000	$ 281,000		986,000	$ 41,156,000
Share of profit	(1,766,000)	$ (1,118,000)		(3,370,000)	(2,753,000)
Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 505,297,000			505,297,000		480,544,000
Partnership profit (loss)				(5,753,000)		(8,573,000)
Real Estate Partnership Net Income Loss [Member]
Schedule of Equity Method Investments [Line Items]
Share of profit				$ (3,370,000)		$ (5,754,000)
Brooksville Quarry L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%			50.00%		50.00%
Total investments	$ 7,546,000			$ 7,546,000		$ 7,488,000
Partnership profit (loss)				(42,000)		(82,000)
Share of profit				(21,000)		(41,000)
Brooksville Quarry L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 14,461,000			$ 14,461,000		$ 14,301,000
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%		50.00%
Total investments	$ 5,485,000			$ 5,485,000		$ 5,530,000
Partnership profit (loss)				(90,000)		(230,000)
Share of profit				(45,000)		(115,000)
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	$ 22,115,000			$ 22,115,000		$ 22,470,000
Bryant Street Partnerships [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	61.36%			61.36%		61.36%
Total investments	$ 58,253,000			$ 58,253,000		$ 59,558,000
Partnership profit (loss)				(4,787,000)		(6,084,000)
Share of profit				(3,186,000)		(4,954,000)
[custom:InterestIncomePreferred]			$ 234,000	236,000
[custom:GuaranteeLiabilityAmortization]					$ 236,000
Bryant Street Partnerships [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	203,480,000			203,480,000		204,082,000
Aberdeen Station [Member]
Schedule of Equity Method Investments [Line Items]
Total investments	917,000			917,000		514,000
Partnership profit (loss)				0		0
Share of profit				0		0
Aberdeen Station [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 917,000			$ 917,000		$ 514,000
D S T Hickory Creek [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	26.65%			26.65%		26.65%
Total investments	$ 6,000,000			$ 6,000,000		$ 6,000,000
Partnership profit (loss)				(271,000)		(481,000)
Share of profit				171,000		343,000
D S T Hickory Creek [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	45,186,000			45,186,000		46,048,000
Amber Ridge Loan [Member]
Schedule of Equity Method Investments [Line Items]
Total investments	6,234,000			6,234,000		11,466,000
Partnership profit (loss)				0		0
Amber Ridge Loan [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 6,234,000			$ 6,234,000		$ 11,466,000
Half St Owner L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	61.37%			61.37%		61.37%
Total investments	$ 39,112,000			$ 39,112,000		$ 38,693,000
Partnership profit (loss)				0		12,000
Share of profit				(64,000)		20,000
Half St Owner L L C [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	$ 119,957,000			$ 119,957,000		$ 93,932,000
Greenville Woodfield Partnerships [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	40.00%			40.00%		40.00%
Total investments	$ 16,108,000			$ 16,108,000		$ 16,194,000
Partnership profit (loss)				(563,000)		(948,000)
Share of profit				(225,000)		(379,000)
Greenville Woodfield Partnerships [Member] | Real Estate Total Assets [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of the partnership	92,947,000			92,947,000		87,731,000
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
Total assets of the partnership			$ 150,082,000
Partnership profit (loss)						(760,000)
Share of profit						(628,000)
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			$ 0		$ 0