DEBT - Narrative (Details)	1 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($) property extension	Dec. 31, 2019 USD ($) property loan extension	Dec. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)
Line of Credit Facility [Line Items]
Number of real estate properties, unencumbered by mortgages | property	45	45
Amount available	$ 6,000,000.0	$ 6,000,000.0
Revolving lines of credit	50,079,000	50,079,000	$ 57,500,000	$ 124,000,000
Carrying principal value	$ 651,455,000	$ 651,455,000	$ 648,474,000	$ 706,140,000
Domestic Line of Credit | Minimum | Base Rate
Line of Credit Facility [Line Items]
Interest rate spread	0.35%
Domestic Line of Credit | Minimum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Interest rate spread	1.35%
Domestic Line of Credit | Maximum | Base Rate
Line of Credit Facility [Line Items]
Interest rate spread	8.50%
Domestic Line of Credit | Maximum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Interest rate spread	1.90%
Multifamily
Line of Credit Facility [Line Items]
Number of apartment communities, serving as collateral for mortgage loans | property	24	24
Mortgages
Line of Credit Facility [Line Items]
Number of loans in default | loan		0
Original principal balance	$ 59,900,000	$ 59,900,000
Stated interest rate	3.88%	3.88%
Weighted average interest rate (in hundredths)	4.02%	4.02%	4.58%	4.69%
Mortgages | Minimum
Line of Credit Facility [Line Items]
Interest rate	3.47%	3.47%
Mortgages | Maximum
Line of Credit Facility [Line Items]
Interest rate	5.73%	5.73%
Line of Credit
Line of Credit Facility [Line Items]
Term	1 year
Unsecured Debt
Line of Credit Facility [Line Items]
Original principal balance	$ 150,000,000.0	$ 150,000,000.0
Note Maturing 2029 | Unsecured Debt
Line of Credit Facility [Line Items]
Original principal balance	$ 75,000,000.0	$ 75,000,000.0
Stated interest rate	3.84%	3.84%
Note Maturing 2028 | Unsecured Debt
Line of Credit Facility [Line Items]
Original principal balance	$ 50,000,000.0	$ 50,000,000.0
Stated interest rate	3.69%	3.69%
Remaining amount under private shelf agreement	$ 25,000,000.0	$ 25,000,000.0
BMO Line of Credit | Line of Credit
Line of Credit Facility [Line Items]
Amount available	$ 250,000,000.0	$ 250,000,000.0		$ 300,000,000.0
Revolving lines of credit			$ 57,500,000	$ 124,000,000.0
Number of extensions | extension	1	1
Extension term		12 months
BMO Line of Credit | Domestic Line of Credit
Line of Credit Facility [Line Items]
Amount available	$ 250,000,000.0	$ 250,000,000.0
Remaining borrowing capacity	199,900,000	199,900,000
Revolving lines of credit	50,100,000	$ 50,100,000
Interest rate		3.81%
UAP Line of Credit | Line of Credit
Line of Credit Facility [Line Items]
Amount available			$ 232,500,000
Term Loan Maturing 2024 | Unsecured Debt
Line of Credit Facility [Line Items]
Original principal balance	70,000,000.0	$ 70,000,000.0
Term Loan Maturing 2025 | Unsecured Debt
Line of Credit Facility [Line Items]
Original principal balance	$ 75,000,000.0	$ 75,000,000.0
Multi-family Residential Properties
Line of Credit Facility [Line Items]
Number of apartment communities | property	69	69