ACQUISITIONS AND DISPOSITIONS - Disposals (Details) $ in Thousands						3 Months Ended		6 Months Ended
	Jun. 23, 2017 USD ($) apartment	Jun. 20, 2017 USD ($) ft²	Jun. 08, 2017 USD ($) ft²	May 30, 2017 USD ($) apartment	Mar. 28, 2017 USD ($) ft²	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Disposed Property Information
Sales Price								$ 0	$ 642,886
Gain on sale of real estate						$ 0	$ 116,283	$ 0	$ 304,017
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disposals
Ownership sold, percentage									100.00%
Assets
Investments in real estate, net							319,078		$ 319,078
Deferred rent receivable and charges, net							22,089		22,089
Other intangible assets, net							129		129
Other assets							38		38
Total assets							341,334		341,334
Liabilities
Debt, net							64,777		64,777
Intangible liabilities, net							1,800		1,800
Total liabilities							66,577		66,577
Additional Information
Premium on assumed mortgage							$ 665		$ 665
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 211 Main Street, San Francisco, CA
Disposed Property Information
Square Feet | ft²					417,266
Sales Price					$ 292,882
Transaction Costs					2,943
Gain on sale of real estate					187,734
Mortgage prepayment penalty					$ 1,508
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 3636 McKinney Avenue, Dallas, TX
Disposed Property Information
Number of units | apartment				103
Sales Price				$ 20,000
Transaction Costs				1,320
Gain on sale of real estate				5,488
Mortgage prepayment penalty				$ 1,143
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 3839 McKinney Avenue, Dallas, TX
Disposed Property Information
Number of units | apartment				75
Sales Price				$ 14,100
Transaction Costs				938
Gain on sale of real estate				4,224
Mortgage prepayment penalty				$ 758
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 200 S College Street, Charlotte, NC
Disposed Property Information
Square Feet | ft²			567,865
Sales Price			$ 148,500
Transaction Costs			833
Gain on sale of real estate			$ 45,906
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 980 9th Street and 1010 8th Street, Sacramento, CA
Disposed Property Information
Square Feet | ft²		485,926
Sales Price		$ 120,500
Transaction Costs		1,119
Gain on sale of real estate		$ 34,559
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 4649 Cole Avenue, Dallas, TX
Disposed Property Information
Number of units | apartment	334
Sales Price	$ 64,000
Transaction Costs	3,311
Gain on sale of real estate	25,836
Mortgage prepayment penalty	$ 2,812