SEGMENT REPORTING - Revenues and Net Operating Income for Reportable Segments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			1
Segment revenues and net operating income [Abstract]
Revenue	$ 46,656	$ 43,910	$ 93,304	$ 88,316
Property operating expenses, including real estate taxes	18,760	17,770	38,001	36,703
Net operating income	27,896	26,140	55,303	51,613
Property management	(2,085)	(1,345)	(3,852)	(2,899)
Casualty gain (loss)	27	(913)	(74)	(1,240)
Depreciation and amortization	(19,308)	(18,156)	(39,300)	(36,316)
General and administrative expenses	(3,797)	(3,202)	(7,703)	(6,630)
Interest expense	(7,089)	(6,940)	(14,320)	(13,851)
Interest and other income (loss)	619	521	1,050	(2,256)
Income (loss) before gain (loss) on sale of real estate and other investments	(3,737)	(3,895)	(8,896)	(11,579)
Gain (loss) on sale of real estate and other investments	26,840	(190)	26,840	(190)
Net income (loss)	23,103	(4,085)	17,944	(11,769)
Multifamily
Segment revenues and net operating income [Abstract]
Revenue	44,957	40,213	89,198	80,258
Property operating expenses, including real estate taxes	17,967	15,952	35,841	32,726
Net operating income	26,990	24,261	53,357	47,532
All Other
Segment revenues and net operating income [Abstract]
Revenue	1,699	3,697	4,106	8,058
Property operating expenses, including real estate taxes	793	1,818	2,160	3,977
Net operating income	$ 906	$ 1,879	$ 1,946	$ 4,081