REAL ESTATE HELD FOR INVESTMENT - Schedule of Real Estate Investments (Details) - USD ($) $ in Thousands			6 Months Ended
	Jan. 08, 2019	Sep. 07, 2016	Jun. 30, 2020	Jul. 01, 2020	Dec. 31, 2019
Real Estate Properties [Line Items]
Total real estate, cost			$ 849,230		$ 824,860
Accumulated depreciation and amortization			(80,816)		(65,381)
Total real estate, net			768,414		759,479
PORT OP LP | Subsequent Event | Battery Point | BPT Holdings, LLC
Real Estate Properties [Line Items]
Percent of outstanding common equity units received in transaction				4.50%
Preferred Class A | Subsidiary of Common Parent
Real Estate Properties [Line Items]
Non-voting preferred membership units sold		820
Interest rate on Class A non-voting preferred membership units		10.00%
Proceeds from sale of units		$ 800
Preferred Class A-2 | Subsidiary of Common Parent
Real Estate Properties [Line Items]
Non-voting preferred membership units sold	1,927
Interest rate on Class A non-voting preferred membership units	10.00%
Proceeds from sale of units	$ 1,900
Total Richardson Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			46,526
Accumulated depreciation and amortization			(12,882)
Total real estate, net			$ 33,644
Palisades Central I
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 23, 2011
Total real estate, cost			$ 13,555
Accumulated depreciation and amortization			(3,991)
Total real estate, net			$ 9,564
Ownership %			90.00%
Palisades Central II
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 23, 2011
Total real estate, cost			$ 22,222
Accumulated depreciation and amortization			(6,199)
Total real estate, net			$ 16,023
Ownership %			90.00%
Greenway I
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 23, 2011
Total real estate, cost			$ 3,017
Accumulated depreciation and amortization			(1,147)
Total real estate, net			$ 1,870
Ownership %			90.00%
Greenway III
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 23, 2011
Total real estate, cost			$ 4,598
Accumulated depreciation and amortization			(1,545)
Total real estate, net			$ 3,053
Ownership %			90.00%
Undeveloped Land
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 23, 2011
Total real estate, cost			$ 3,134
Accumulated depreciation and amortization			0
Total real estate, net			$ 3,134
Ownership %			90.00%
Park Highlands
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Dec. 30, 2011
Total real estate, cost			$ 36,315
Accumulated depreciation and amortization			0
Total real estate, net			$ 36,315
Ownership %			100.00%
Park Centre
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Mar. 28, 2013
Total real estate, cost			$ 38,017
Accumulated depreciation and amortization			(7,586)
Total real estate, net			$ 30,431
Ownership %			100.00%
1180 Raymond
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Aug. 20, 2013
Total real estate, cost			$ 47,486
Accumulated depreciation and amortization			(8,537)
Total real estate, net			$ 38,949
Ownership %			100.00%
Park Highlands II
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Dec. 10, 2013
Total real estate, cost			$ 27,622
Accumulated depreciation and amortization			0
Total real estate, net			$ 27,622
Ownership %			100.00%
Richardson Land II
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Sep. 04, 2014
Total real estate, cost			$ 3,418
Accumulated depreciation and amortization			0
Total real estate, net			$ 3,418
Ownership %			90.00%
Crown Pointe
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Feb. 14, 2017
Total real estate, cost			$ 96,455
Accumulated depreciation and amortization			(13,487)
Total real estate, net			$ 82,968
Ownership %			100.00%
The Marq
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Mar. 01, 2018
Total real estate, cost			$ 95,525
Accumulated depreciation and amortization			(8,612)
Total real estate, net			$ 86,913
Ownership %			100.00%
City Tower
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Mar. 06, 2018
Total real estate, cost			$ 157,413
Accumulated depreciation and amortization			(15,659)
Total real estate, net			$ 141,754
Ownership %			100.00%
Eight & Nine Corporate Centre
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Jun. 08, 2018
Total real estate, cost			$ 79,839
Accumulated depreciation and amortization			(5,861)
Total real estate, net			$ 73,978
Ownership %			100.00%
Georgia 400 Center
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			May 23, 2019
Total real estate, cost			$ 92,418
Accumulated depreciation and amortization			(5,347)
Total real estate, net			$ 87,071
Ownership %			100.00%
Birmingham Homes
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 04, 2019
Total real estate, cost			$ 13,768
Accumulated depreciation and amortization			(292)
Total real estate, net			$ 13,476
Ownership %			100.00%
Houston Homes
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 04, 2019
Total real estate, cost			$ 29,409
Accumulated depreciation and amortization			(666)
Total real estate, net			$ 28,743
Ownership %			100.00%
Jacksonville Homes
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 04, 2019
Total real estate, cost			$ 27,592
Accumulated depreciation and amortization			(647)
Total real estate, net			$ 26,945
Ownership %			100.00%
Memphis Homes
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 04, 2019
Total real estate, cost			$ 18,754
Accumulated depreciation and amortization			(426)
Total real estate, net			$ 18,328
Ownership %			100.00%
Atlanta Homes
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 04, 2019
Total real estate, cost			$ 4,732
Accumulated depreciation and amortization			(120)
Total real estate, net			$ 4,612
Ownership %			100.00%
Oklahoma Homes
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			Nov. 04, 2019
Total real estate, cost			$ 16,697
Accumulated depreciation and amortization			(411)
Total real estate, net			$ 16,286
Ownership %			100.00%
Illinois Homes
Real Estate Properties [Line Items]
Date Acquired or Foreclosed on			May 28, 2020
Total real estate, cost			$ 17,244
Accumulated depreciation and amortization			(283)
Total real estate, net			$ 16,961
Ownership %			100.00%
Single Family Home Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			$ 128,196
Accumulated depreciation and amortization			(2,845)
Total real estate, net			125,351
Land
Real Estate Properties [Line Items]
Total real estate, cost			181,392		175,317
Land | Total Richardson Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			6,244
Land | Palisades Central I
Real Estate Properties [Line Items]
Total real estate, cost			1,037
Land | Palisades Central II
Real Estate Properties [Line Items]
Total real estate, cost			810
Land | Greenway I
Real Estate Properties [Line Items]
Total real estate, cost			561
Land | Greenway III
Real Estate Properties [Line Items]
Total real estate, cost			702
Land | Undeveloped Land
Real Estate Properties [Line Items]
Total real estate, cost			3,134
Land | Park Highlands
Real Estate Properties [Line Items]
Total real estate, cost			36,315
Land | Park Centre
Real Estate Properties [Line Items]
Total real estate, cost			3,251
Land | 1180 Raymond
Real Estate Properties [Line Items]
Total real estate, cost			8,292
Land | Park Highlands II
Real Estate Properties [Line Items]
Total real estate, cost			27,622
Land | Richardson Land II
Real Estate Properties [Line Items]
Total real estate, cost			3,418
Land | Crown Pointe
Real Estate Properties [Line Items]
Total real estate, cost			22,590
Land | The Marq
Real Estate Properties [Line Items]
Total real estate, cost			10,387
Land | City Tower
Real Estate Properties [Line Items]
Total real estate, cost			13,930
Land | Eight & Nine Corporate Centre
Real Estate Properties [Line Items]
Total real estate, cost			17,401
Land | Georgia 400 Center
Real Estate Properties [Line Items]
Total real estate, cost			11,431
Land | Birmingham Homes
Real Estate Properties [Line Items]
Total real estate, cost			2,444
Land | Houston Homes
Real Estate Properties [Line Items]
Total real estate, cost			6,154
Land | Jacksonville Homes
Real Estate Properties [Line Items]
Total real estate, cost			2,986
Land | Memphis Homes
Real Estate Properties [Line Items]
Total real estate, cost			2,679
Land | Atlanta Homes
Real Estate Properties [Line Items]
Total real estate, cost			783
Land | Oklahoma Homes
Real Estate Properties [Line Items]
Total real estate, cost			2,082
Land | Illinois Homes
Real Estate Properties [Line Items]
Total real estate, cost			3,383
Land | Single Family Home Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			20,511
Buildings and improvements
Real Estate Properties [Line Items]
Total real estate, cost			639,060		618,974
Buildings and improvements | Total Richardson Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			40,282
Buildings and improvements | Palisades Central I
Real Estate Properties [Line Items]
Total real estate, cost			12,518
Buildings and improvements | Palisades Central II
Real Estate Properties [Line Items]
Total real estate, cost			21,412
Buildings and improvements | Greenway I
Real Estate Properties [Line Items]
Total real estate, cost			2,456
Buildings and improvements | Greenway III
Real Estate Properties [Line Items]
Total real estate, cost			3,896
Buildings and improvements | Undeveloped Land
Real Estate Properties [Line Items]
Total real estate, cost			0
Buildings and improvements | Park Highlands
Real Estate Properties [Line Items]
Total real estate, cost			0
Buildings and improvements | Park Centre
Real Estate Properties [Line Items]
Total real estate, cost			34,766
Buildings and improvements | 1180 Raymond
Real Estate Properties [Line Items]
Total real estate, cost			39,194
Buildings and improvements | Park Highlands II
Real Estate Properties [Line Items]
Total real estate, cost			0
Buildings and improvements | Richardson Land II
Real Estate Properties [Line Items]
Total real estate, cost			0
Buildings and improvements | Crown Pointe
Real Estate Properties [Line Items]
Total real estate, cost			69,661
Buildings and improvements | The Marq
Real Estate Properties [Line Items]
Total real estate, cost			81,587
Buildings and improvements | City Tower
Real Estate Properties [Line Items]
Total real estate, cost			136,184
Buildings and improvements | Eight & Nine Corporate Centre
Real Estate Properties [Line Items]
Total real estate, cost			57,920
Buildings and improvements | Georgia 400 Center
Real Estate Properties [Line Items]
Total real estate, cost			73,521
Buildings and improvements | Birmingham Homes
Real Estate Properties [Line Items]
Total real estate, cost			11,162
Buildings and improvements | Houston Homes
Real Estate Properties [Line Items]
Total real estate, cost			22,823
Buildings and improvements | Jacksonville Homes
Real Estate Properties [Line Items]
Total real estate, cost			24,253
Buildings and improvements | Memphis Homes
Real Estate Properties [Line Items]
Total real estate, cost			15,809
Buildings and improvements | Atlanta Homes
Real Estate Properties [Line Items]
Total real estate, cost			3,884
Buildings and improvements | Oklahoma Homes
Real Estate Properties [Line Items]
Total real estate, cost			14,416
Buildings and improvements | Illinois Homes
Real Estate Properties [Line Items]
Total real estate, cost			13,598
Buildings and improvements | Single Family Home Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			105,945
Tenant origination and absorption costs
Real Estate Properties [Line Items]
Total real estate, cost			28,778		$ 30,569
Tenant origination and absorption costs | Total Richardson Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Palisades Central I
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Palisades Central II
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Greenway I
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Greenway III
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Undeveloped Land
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Park Highlands
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Park Centre
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | 1180 Raymond
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Park Highlands II
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Richardson Land II
Real Estate Properties [Line Items]
Total real estate, cost			0
Tenant origination and absorption costs | Crown Pointe
Real Estate Properties [Line Items]
Total real estate, cost			4,204
Tenant origination and absorption costs | The Marq
Real Estate Properties [Line Items]
Total real estate, cost			3,551
Tenant origination and absorption costs | City Tower
Real Estate Properties [Line Items]
Total real estate, cost			7,299
Tenant origination and absorption costs | Eight & Nine Corporate Centre
Real Estate Properties [Line Items]
Total real estate, cost			4,518
Tenant origination and absorption costs | Georgia 400 Center
Real Estate Properties [Line Items]
Total real estate, cost			7,466
Tenant origination and absorption costs | Birmingham Homes
Real Estate Properties [Line Items]
Total real estate, cost			162
Tenant origination and absorption costs | Houston Homes
Real Estate Properties [Line Items]
Total real estate, cost			432
Tenant origination and absorption costs | Jacksonville Homes
Real Estate Properties [Line Items]
Total real estate, cost			353
Tenant origination and absorption costs | Memphis Homes
Real Estate Properties [Line Items]
Total real estate, cost			266
Tenant origination and absorption costs | Atlanta Homes
Real Estate Properties [Line Items]
Total real estate, cost			65
Tenant origination and absorption costs | Oklahoma Homes
Real Estate Properties [Line Items]
Total real estate, cost			199
Tenant origination and absorption costs | Illinois Homes
Real Estate Properties [Line Items]
Total real estate, cost			263
Tenant origination and absorption costs | Single Family Home Portfolio
Real Estate Properties [Line Items]
Total real estate, cost			$ 1,740