Real Estate Property Asset Acquisitions (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Real Estate [Line Items]
Acquired in-place leases, net	$ 8,371	$ 9,835
Prepaid expenses, deposits and other	5,945	5,853
TOTAL ASSETS	2,259,864	1,986,933
Accounts payable and accrued expenses	38,069	32,401
Security deposits payable	6,570	6,114
Other liabilities and deferred credits	46,061	48,337
Liabilities	1,415,720	$ 1,148,382
Gateway Marketplace
Real Estate [Line Items]
Land	17,363
Buildings	19,192
Land improvements	1,522
Furniture, fixtures, and equipment	930
Total real estate	39,007
Acquired in-place leases, net	2,920
Prepaid expenses, deposits and other	0
TOTAL ASSETS	41,927
Accounts payable and accrued expenses	203
Security deposits payable	22
Other liabilities and deferred credits	1,034
Liabilities	1,259
Pacific Ridge Apartments
Real Estate [Line Items]
Land	47,971
Buildings	171,813
Land improvements	3,403
Furniture, fixtures, and equipment	3,281
Total real estate	226,468
Acquired in-place leases, net	5,592
Prepaid expenses, deposits and other	424
TOTAL ASSETS	232,484
Accounts payable and accrued expenses	74
Security deposits payable	673
Other liabilities and deferred credits	49
Liabilities	$ 796