INVESTMENT IN UNCONSOLIDATED JOINT VENTURES - Summarized Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Real estate assets, net of accumulated depreciation and amortization	$ 755,460		$ 759,479
Total assets	1,042,919		1,041,242
Other liabilities	20,419		19,801
Total liabilities, mezzanine equity and equity	1,042,919		1,041,242
Income Statement [Abstract]
Revenues	24,601	$ 21,911
Real estate taxes and insurance	3,428	2,977
Depreciation and amortization	8,984	7,681
Interest expense	6,796	7,168
Total expenses	16,436	30,337
Net (loss) income attributable to common stockholders	(17,972)	16,781
110 William Joint Venture
Balance Sheet Related Disclosures [Abstract]
Real estate assets, net of accumulated depreciation and amortization	247,711		242,430
Other assets	36,201		35,747
Total assets	283,912		278,177
Notes payable, net	301,186		292,221
Other liabilities	10,125		10,664
Partners’ deficit	(27,399)		(24,708)
Total liabilities, mezzanine equity and equity	283,912		278,177
Income Statement [Abstract]
Revenues	7,982	8,259
Real estate taxes and insurance	1,823	1,706
Depreciation and amortization	2,643	2,665
Interest expense	3,926	4,608
Total expenses	10,694	11,150
Total other income	22	33
Net (loss) income attributable to common stockholders	(2,690)	(2,858)
Company’s share of net loss	(1,614)	(1,715)
Company’s equity in income (loss) of unconsolidated joint venture		7,800
Loss from equity method investments		300
110 William Joint Venture | Operating, maintenance, and management
Income Statement [Abstract]
Expenses	2,302	2,171
353 Sacramento Joint Venture
Balance Sheet Related Disclosures [Abstract]
Real estate assets, net of accumulated depreciation and amortization	183,446		180,592
Other assets	17,073		21,822
Total assets	200,519		202,414
Notes payable, net	115,353		115,280
Other liabilities	8,694		11,193
Partners’ deficit	76,472		75,941
Total liabilities, mezzanine equity and equity	200,519		$ 202,414
Income Statement [Abstract]
Revenues	4,887	4,157
Real estate taxes and insurance	753	700
Depreciation and amortization	1,603	1,567
Interest expense	1,321	1,419
Total expenses	4,357	4,517
Net (loss) income attributable to common stockholders	530	(360)
Company’s equity in income (loss) of unconsolidated joint venture	328	(163)
353 Sacramento Joint Venture | Operating, maintenance, and management
Income Statement [Abstract]
Expenses	$ 680	$ 831