SCHEDULE IV - MORTGAGE LOANS - Schedule of Mortgage Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Face Amount	130,626
Carrying Value	130,626	$ 143,087	$ 114,893	$ 102,143
Convertible loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face Amount	31,635
Carrying Value	$ 31,635
Convertible loans | Autumn Breeze
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	1,867
Carrying Value	$ 1,867
Convertible loans | Bellwether Ridge
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	3,858
Carrying Value	$ 3,858
Convertible loans | Forest Pines
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	2,869
Carrying Value	$ 2,869
Convertible loans | Parc at Ingleside
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	2,523
Carrying Value	$ 2,523
Convertible loans | Parc at Windmill Farms
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	7,803
Carrying Value	$ 7,803
Convertible loans | Plum Tree
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	857
Carrying Value	$ 857
Convertible loans | Spyglass of Ennis
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	5,360
Carrying Value	$ 5,360
Convertible loans | Steeple Crest
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	6,498
Carrying Value	6,498
Land loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face Amount	31,201
Carrying Value	$ 31,201
Land loans | ABC Land and Development, Inc.
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.50%
Prior Liens	$ 0
Face Amount	4,408
Carrying Value	$ 4,408
Land loans | ABC Paradise, LLC
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.50%
Prior Liens	$ 0
Face Amount	1,210
Carrying Value	$ 1,210
Land loans | Lake Wales
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.50%
Prior Liens	$ 0
Face Amount	3,000
Carrying Value	$ 3,000
Land loans | Legacy Pleasant Grove
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	496
Carrying Value	$ 496
Land loans | McKinney Ranch
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	6.00%
Prior Liens	$ 0
Face Amount	4,554
Carrying Value	$ 4,554
Land loans | One Realco Land Holding, Inc.
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.50%
Prior Liens	$ 0
Face Amount	1,728
Carrying Value	$ 1,728
Land loans | Riverview on the Park Land, LLC
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	9.50%
Prior Liens	$ 0
Face Amount	1,045
Carrying Value	$ 1,045
Land loans | RNC Portfolio, Inc.
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	5.00%
Prior Liens	$ 0
Face Amount	8,853
Carrying Value	$ 8,853
Land loans | Spartan Land
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	5,907
Carrying Value	5,907
Subsidized housing
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Face Amount	67,790
Carrying Value	$ 67,790
Subsidized housing | Phillips Foundation for Better Living, Inc.
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	61
Carrying Value	$ 61
Subsidized housing | Unified Housing Foundation Inc., Maturing July 31, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	2,880
Carrying Value	$ 2,880
Subsidized housing | Unified Housing Foundation Inc ., Maturing August 30, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	212
Carrying Value	$ 212
Subsidized housing | Unified Housing Foundation Inc., Maturing October 31, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	6,831
Carrying Value	$ 6,831
Subsidized housing | Unified Housing Foundation Inc., Maturing December 31, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	10,896
Carrying Value	$ 10,896
Subsidized housing | Unified Housing Foundation Inc., Maturing March 31, 2022
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	10,096
Carrying Value	$ 10,096
Subsidized housing | Unified Housing Foundation Inc., Maturing March 31, 2023
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	6,990
Carrying Value	$ 6,990
Subsidized housing | Unified Housing Foundation Inc., Maturing May 31, 2023
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	3,615
Carrying Value	$ 3,615
Subsidized housing | Unified Housing Foundation Inc., Maturing December 31, 2032
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Rate	12.00%
Prior Liens	$ 0
Face Amount	26,209
Carrying Value	$ 26,209