REAL ESTATE Property Asset Acquisitions (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Real Estate [Line Items]
Lease intangibles	$ 9,052	$ 9,835
Prepaid expenses and other	5,775	5,853
TOTAL ASSETS	2,275,618	1,986,933
Accounts payable and accrued expenses	48,107	32,401
Security deposits payable	6,736	6,114
Other liabilities and deferred credits, net	47,423	48,337
Total liabilities	1,427,067	$ 1,148,382
Pacific Ridge
Real Estate [Line Items]
Land	47,972
Building	171,813
Land improvements	3,403
Furniture, fixtures, and equipment	3,281
Total real estate	226,469
Lease intangibles	5,592
Prepaid expenses and other	424
TOTAL ASSETS	232,485
Accounts payable and accrued expenses	74
Security deposits payable	673
Other liabilities and deferred credits, net	49
Total liabilities	796
Gateway Marketplace
Real Estate [Line Items]
Land	17,363
Building	19,192
Land improvements	1,522
Furniture, fixtures, and equipment	930
Total real estate	39,007
Lease intangibles	2,920
Prepaid expenses and other	0
TOTAL ASSETS	41,927
Accounts payable and accrued expenses	203
Security deposits payable	22
Other liabilities and deferred credits, net	1,034
Total liabilities	$ 1,259