Mortgages and Other Notes Payable - Schedule of Debt (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Mar. 04, 2021	Mar. 05, 2020 a	Dec. 31, 2019 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 236,069			$ 241,527
EQK Portage - Land
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Area of land (acres) | a			49.2
Mortgages and other notes payable
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	236,069			241,527
Mortgages and other notes payable | 600 Las Colinas
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 35,589			36,302
Interest Rate	5.30%
Mortgages and other notes payable | 770 South Post Oak
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 11,871			12,077
Interest Rate	4.40%
Mortgages and other notes payable | Bridge View Plaza
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 0			3,824
Interest Rate	7.75%
Mortgages and other notes payable | Chelsea
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 8,194			8,749
Interest Rate	3.40%
Mortgages and other notes payable | EQK Portage - Land
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 3,350			0
Interest Rate	10.00%
Mortgages and other notes payable | HSW Partners
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 14,690			13,032
Interest Rate	9.50%
Mortgages and other notes payable | Farnham Park
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 0			9,144
Interest Rate	3.39%
Mortgages and other notes payable | Forest Grove
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 7,333			1,390
Interest Rate	3.75%
Mortgages and other notes payable | Forest Grove | Prime Rate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Variable interest rate	0.50%
Mortgages and other notes payable | Landing Bayou
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 14,643			15,467
Interest Rate	3.50%
Mortgages and other notes payable | Athens
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 1,155			1,155
Interest Rate	5.90%
Mortgages and other notes payable | Legacy at Pleasant Grove
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 13,653			13,944
Interest Rate	3.60%
Mortgages and other notes payable | McKinney 36 Land
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 820			944
Interest Rate	8.00%
Mortgages and other notes payable | Overlook at Allenville Phase II
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 15,621			15,798
Interest Rate	3.80%
Mortgages and other notes payable | Parc at Denham Springs Phase II
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 16,128			14,785
Interest Rate	4.10%
Mortgages and other notes payable | Stanford Center
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 39,093			39,255
Interest Rate	6.00%
Mortgages and other notes payable | Sugar Mill Phase III
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 9,298			5,908
Interest Rate	4.50%
Mortgages and other notes payable | Toulon
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 13,975			14,219
Interest Rate	3.20%
Mortgages and other notes payable | Villager
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 0			556
Interest Rate	2.50%
Mortgages and other notes payable | Villas at Bon Secour
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 10,280			11,026
Interest Rate	4.00%
Mortgages and other notes payable | Vista Ridge
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 9,979			10,122
Interest Rate	4.00%
Mortgages and other notes payable | Windmill Farms
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgages and other notes payable	$ 10,397			$ 13,830
Interest Rate	6.00%
Mortgages and other notes payable | Windmill Farms | Subsequent Event
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate		5.00%