RELATED PARTY MANAGEMENT SERVICES BUSINESS - General Information (Details) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 26, 2019 USD ($) property shares	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Real Estate [Line Items]
Outstanding Principal		$ 235,688		$ 235,688		$ 280,500
Gain (Loss) on Extinguishment of Debt				(641)	$ 1,141
Land JV
Real Estate [Line Items]
Management fee revenue earned		30	$ 50	90	200
Management fee revenue earned per month				20
Monthly management fee				$ 10
Management Agreement PINE
Real Estate [Line Items]
Percentage of base management fee				0.375%
Management fee (as a percent)				1.50%
Percentage of cumulative annual hurdle rate				8.00%
Amount of threshold incentive fee				$ 0
Percentage of multiply factor				15.00%
Amount of incentive fee						$ 0
Management fee revenue earned		900	600	$ 2,300	1,900
Proceeds from Dividends Received		500	$ 400	1,500	$ 1,200
Alpine
Real Estate [Line Items]
Number of properties sold | property	15
Aggregate cash consideration	$ 125,900
Alpine | Mortgage Notes Payable Under CMBS Portfolio
Real Estate [Line Items]
Real estate acquired purchase price				44,500
Outstanding Principal		$ 30,000		30,000
Gain (Loss) on Extinguishment of Debt				(500)
Alpine | Mortgage Notes Payable Under CMBS Portfolio | Income Property Single Tenant
Real Estate [Line Items]
Real estate acquired purchase price				$ 11,500
Alpine | IPO Purchase
Real Estate [Line Items]
Number of contributed properties | property	5
Aggregate of OP units | shares	1,223,854
Initial value	$ 23,300