SUPPLEMENTAL CASH FLOW AND SIGNIFICANT NONCASH TRANSACTION DISCLOSURES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Disclosure of Cash Flow Information:
Interest paid, net of capitalized interest of $2,739, $2,565 and $2,339 for the years ended December 31, 2019, 2018 and 2017, respectively	$ 25,703	$ 27,029	$ 32,688
Interest costs capitalized	2,739	2,565	2,339
Assets and liabilities deconsolidated in connection with the 353 Sacramento partial sale:
Real estate, net	759,479	552,974
Rents and other receivables, net	16,593	10,876
Prepaid Expense and Other Assets	13,988	11,782
Accounts payable and accrued liabilities	21,329	19,506
Below-market leases, net	3,180	3,528
Other liabilities	19,801	21,006
Assets and liabilities consolidated in connection with the PORT acquisition:
Acquisition fees due to affiliates on investment in unconsolidated entities	137	0	0
Accrued improvements to real estate	5,302	3,363	3,717
Redeemable common stock payable	829	10,000	8,595
Restricted stock payable	16,320	0	0
Mezzanine equity in connection with subordinated performance fee due upon termination	10,880	0	0
Restricted stock (additional paid in capital) in connection with subordinated performance fee due upon termination	5,440	0	0
Mortgage loan assumed by buyer in connection with sale of real estate	23,663	0	0
Redemptions of Series B Preferred Units in exchange for Series A-3 Preferred Units	2,992	0	0
Distributions paid to common stockholders through common stock issuances pursuant to the dividend reinvestment plan	829	1,418	8,666
Distributions paid to common stockholders through common stock issuances pursuant to the December 2017 special dividend	0	150,299	0
Distributions paid to common stockholders through common stock issuances pursuant to the November 2018 special dividend	0	127,911	0
PORT
Assets and liabilities consolidated in connection with the PORT acquisition:
Cash	8,104	0	0
Restricted cash	1,667	0	0
Rents and other receivables	989	0	0
Prepaid expenses and other assets	634	0	0
Real estate held for investment	109,922	0	0
Notes payable	61,885	0	0
Accounts payable and accrued liabilities	1,893	0	0
Other liabilities	904	0	0
353 Sacramento
Assets and liabilities deconsolidated in connection with the 353 Sacramento partial sale:
Real estate, net	0	0	170,586
Rents and other receivables, net	0	0	1,244
Prepaid Expense and Other Assets	0	0	555
Notes payable, net	0	0	87,132
Accounts payable and accrued liabilities	0	0	1,574
Below-market leases, net	0	0	2,960
Other liabilities	$ 0	$ 0	$ 924