INVESTMENT IN UNCONSOLIDATED JOINT VENTURES (Battery Point Restructuring) (Details) - USD ($)				3 Months Ended	12 Months Ended
	Jul. 01, 2020	Oct. 29, 2019	Mar. 20, 2019	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 12, 2017	Oct. 28, 2016
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated entities					$ 79,666,000	$ 78,276,000
BPT Holdings, LLC | Subsidiaries | Battery Point Trust Inc.
Schedule of Equity Method Investments [Line Items]
Common equity units received in transaction	510,816
Percent of outstanding common equity units received in transaction	4.50%
Common equity units received in transaction	$ 3,000,000.0
Battery Point Trust Inc.
Schedule of Equity Method Investments [Line Items]
Common stock, shares acquired (in shares)	1,000,000
Battery Point Holdings | DayMark
Schedule of Equity Method Investments [Line Items]
Noncontrolling interest			40.00%
DayMark Service Entities
Schedule of Equity Method Investments [Line Items]
Property management fee, percent of gross asset value fee			1.50%
Annual property management fee, percent of tenants rent received fee			8.00%
Acquisition fee, percent of purchase price fee			1.00%
Commission fee from sales as broker			1.00%
Battery Point
Schedule of Equity Method Investments [Line Items]
Number of securities received (in shares)			210,000
Price per share (in dollars per share)			$ 25
Battery Point | Series B Preferred Units
Schedule of Equity Method Investments [Line Items]
Investments to be made								$ 17,500,000
Investments						$ 4,500,000	$ 4,500,000
Dividend rate, percentage		12.00%
Redemptions of common stock (in shares)			13,000
Stock redeemed (in dollars per share)			$ 1,000
Battery Point | Series B Preferred Units | Maximum
Schedule of Equity Method Investments [Line Items]
Investments to be made									$ 25,000,000
Battery Point | Series A-3 Preferred Units
Schedule of Equity Method Investments [Line Items]
Principal paydown			$ 8,600,000
Accrued interest and exit fees			$ 900,000
Number of securities received (in shares)						640,000
Stock repurchased during period (in shares)					430,000	430,000
Stock repurchased during period					$ 10,800,000	$ 10,800,000
Number of securities eliminated in consolidation because of acquisition	640,000
Battery Point Series A-3 Preferred Units
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated entities					$ 0	$ 13,991,000
Battery Point Series A-3 Preferred Units | Series A-3 Preferred Units
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated entities	$ 14,000,000.0			$ 14,000,000.0
Gains (losses) on investment of real estate prior to acquisition	$ 2,000,000.0			$ 2,000,000.0