INVESTMENT SECURITIES - Tabular Disclosure (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Cost	$ 38,753,000	$ 38,753,000
Unrealized Losses in Investment Income	(3,345,000)	(8,179,000)
Investment in Alpine Income Property Trust, Inc.	35,408,000	30,574,000
Common Stock
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Cost	15,500,000	15,500,000
Unrealized Losses in Investment Income	(1,338,000)	(3,271,000)
Investment in Alpine Income Property Trust, Inc.	14,162,000	12,229,000
Operating Units
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Cost	23,253,000	23,253,000
Unrealized Losses in Investment Income	(2,007,000)	(4,908,000)
Investment in Alpine Income Property Trust, Inc.	$ 21,246,000	$ 18,345,000