ACQUISITIONS AND DISPOSITIONS - Dispositions (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) property unit	Sep. 30, 2019 USD ($) property unit	Sep. 30, 2020 USD ($) unit	Sep. 30, 2019 USD ($) unit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price		$ 85,000		$ 85,000
Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price	$ 44,300	95,329	$ 44,300	95,329
Book Value and Sales Cost	18,828	$ 55,954	18,828	55,954
Gain/(Loss)			25,472	39,375
Disposed of by Sale | Unimproved Land
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property		1
Sale Price	43,000	$ 4,374	43,000	4,374
Book Value and Sales Cost		4,225		4,225
Gain/(Loss)				149
Disposed of by Sale | Unimproved Land | Rapid City Land - Rapid City, SD
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price	1,300		1,300
Book Value and Sales Cost	$ 1,490		1,490
Gain/(Loss)			(190)
Disposed of by Sale | Unimproved Land | Creekside Crossing - Bismarck, ND
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price		3,049		3,049
Book Value and Sales Cost		3,205		3,205
Gain/(Loss)				(156)
Disposed of by Sale | Unimproved Land | Minot 1525 24th Ave SW - Minot, ND
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price		725		725
Book Value and Sales Cost		593		593
Gain/(Loss)				132
Disposed of by Sale | Unimproved Land | Weston - Weston, WI
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price		600		600
Book Value and Sales Cost		$ 427		427
Gain/(Loss)				173
Disposed of by Sale | Multifamily
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property	4	6
Sale Price	$ 42,500	$ 84,425	42,500	84,425
Book Value and Sales Cost	$ 16,864	$ 45,681	16,864	45,681
Gain/(Loss)			$ 25,636	$ 38,744
Disposed of by Sale | Multifamily | 268 homes - Forest Park - Grand Forks, ND
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit	268		268
Sale Price	$ 19,625		$ 19,625
Book Value and Sales Cost	$ 6,884		6,884
Gain/(Loss)			$ 12,741
Disposed of by Sale | Multifamily | 90 homes - Landmark - Grand Forks, ND
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit	90		90
Sale Price	$ 3,725		$ 3,725
Book Value and Sales Cost	$ 1,348		1,348
Gain/(Loss)			$ 2,377
Disposed of by Sale | Multifamily | 164 homes - Southwind - Grand Forks, ND
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit	164		164
Sale Price	$ 10,850		$ 10,850
Book Value and Sales Cost	$ 4,573		4,573
Gain/(Loss)			$ 6,277
Disposed of by Sale | Multifamily | 168 homes - Valley Park - Grand Forks, ND
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit	168		168
Sale Price	$ 8,300		$ 8,300
Book Value and Sales Cost	$ 4,059		4,059
Gain/(Loss)			4,241
Disposed of by Sale | Multifamily | 21 homes - Pinehurst - Billings, MT
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit		21		21
Sale Price		$ 1,675		$ 1,675
Book Value and Sales Cost		$ 961		961
Gain/(Loss)				$ 714
Disposed of by Sale | Multifamily | 160 homes - Brookfield Village - Topeka, KS
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit		160		160
Sale Price		$ 10,350		$ 10,350
Book Value and Sales Cost		$ 5,853		5,853
Gain/(Loss)				$ 4,497
Disposed of by Sale | Multifamily | 220 homes - Crown Colony - Topeka, KS
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit		220		220
Sale Price		$ 17,200		$ 17,200
Book Value and Sales Cost		$ 7,876		7,876
Gain/(Loss)				$ 9,324
Disposed of by Sale | Multifamily | 54 homes - Mariposa - Topeka, KS
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit		54		54
Sale Price		$ 6,100		$ 6,100
Book Value and Sales Cost		$ 4,290		4,290
Gain/(Loss)				$ 1,810
Disposed of by Sale | Multifamily | 300 homes - Sherwood - Topeka, KS
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit		300		300
Sale Price		$ 26,150		$ 26,150
Book Value and Sales Cost		$ 11,536		11,536
Gain/(Loss)				$ 14,614
Disposed of by Sale | Multifamily | 308 homes - Villa West - Topeka, KS
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of homes | unit		308		308
Sale Price		$ 22,950		$ 22,950
Book Value and Sales Cost		15,165		15,165
Gain/(Loss)				7,785
Disposed of by Sale | Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property	1
Disposed of by Sale | Other | Dakota West
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price	$ 500		500
Book Value and Sales Cost	$ 474		474
Gain/(Loss)			$ 26
Disposed of by Sale | Other | Minot 1400 31st Ave SW - Minot, ND
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Price		6,530		6,530
Book Value and Sales Cost		$ 6,048		6,048
Gain/(Loss)				$ 482