DISCONTINUED OPERATIONS - Effect on Net Income and Gains (Losses) From Sale Of Property (Details) $ in Thousands	3 Months Ended								8 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($) apartment_community property	Dec. 31, 2019 USD ($) apartment_community property	Dec. 31, 2018 USD ($)	Apr. 30, 2018 USD ($) property
REVENUE
Revenues, Total	$ 45,540	$ 44,138	$ 43,910	$ 44,406	$ 45,777	$ 47,436	$ 46,934	$ 45,608	$ 121,871	$ 177,994	$ 185,755	$ 121,871	$ 169,745
EXPENSES
Property operating expenses, excluding real estate taxes									37,198	51,625	57,249		54,292
Real estate taxes									13,521	21,533	21,066		18,742
Property management expense									3,663	5,801	6,186		5,526
Depreciation and amortization									50,456	75,593	74,271		82,070
TOTAL EXPENSES									116,786	169,654	174,338		193,449
Interest expense									(21,359)	(27,525)	(30,537)		(34,178)
Gain (loss) on extinguishment of debt(1)									(556)	(23)	(2,360)		(940)
Gain (loss) on sale of discontinued operations									10,277	25,503	97,624		183,687
INCOME FROM DISCONTINUED OPERATIONS									570	0	0		164,823
Property Sale Data
Gain (loss) on sale of discontinued operations									10,277	$ 25,503	$ 97,624		$ 183,687
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties classified as discontinued operations | property										0	0		27
EXPENSES
Gain (loss) on sale of discontinued operations									0				$ 163,567
Property Sale Data
Sales price									0				437,652
Net book value and sales costs									0				(274,085)
Gain (loss) on sale of discontinued operations									0				163,567
Discontinued Operations, Disposed of by Sale
REVENUE
Real estate rentals, prior to ASC 606 adoption									0				19,744
EXPENSES
Property operating expenses, excluding real estate taxes									0				6,350
Real estate taxes									0				5,191
Depreciation and amortization									0				8,445
TOTAL EXPENSES									0				20,192
Operating income (loss)									0				11,202
Interest expense									0				(4,172)
Gain (loss) on extinguishment of debt(1)									0				(6,508)
Interest income									0				661
Other income									0				73
Income (loss) from discontinued operations before gain on sale									0				1,256
Gain (loss) on sale of discontinued operations									570				163,567
INCOME FROM DISCONTINUED OPERATIONS									570				164,823
Property Sale Data
Gain (loss) on sale of discontinued operations									570				163,567
Discontinued Operations, Disposed of by Sale | All Other
EXPENSES
INCOME FROM DISCONTINUED OPERATIONS									570				164,823
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties classified as held for sale | apartment_community										0	0
Tenant Reimbursement | Discontinued Operations, Disposed of by Sale
REVENUE
Revenues, Total									0				11,650
Real Estate
EXPENSES
Property management expense									50,719	$ 73,158	$ 78,315		73,034
Real Estate | Discontinued Operations, Disposed of by Sale
REVENUE
Revenues, Total									0				31,394
Management Service
EXPENSES
Property management expense									3,663	$ 5,801	$ 6,186		5,526
Management Service | Discontinued Operations, Disposed of by Sale
EXPENSES
Property management expense									$ 0				$ 206