LOANS RECEIVABLE AND OTHER INVESTMENTS - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans receivable investments | loan	20		20
Principal balance	$ 68,486,000		$ 68,486,000		$ 96,492,000
Loan loss reserve	$ 783,000		$ 783,000		$ 1,258,000
Number of loans receivable considered to be impaired | loan					1
Principal balance of impaired loan receivable					$ 1,300,000
Number of loans more than 90 days past due still accruing interest | loan					1
Book value of loans more than 90 days past due and still accruing interest					$ 4,300,000
Nonperforming Financial Instruments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans receivable on nonaccrual status | loan	2		2		2
Book value of loans receivable on nonaccrual status	$ 0		$ 0		$ 1,300,000
Specific Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan loss reserve in period	0	$ 600,000	1,200,000	$ 600,000
Loan loss reserve	0		0		700,000
Portfolio-Based Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in portfolio-based loan loss reserve	100,000	$ 300,000	200,000	$ 600,000
Loan loss reserve	$ 800,000		$ 800,000		$ 600,000
Receivables Acquired with Deteriorated Credit Quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans receivable investments | loan	6		6		7
Principal balance	$ 2,800,000		$ 2,800,000		$ 27,700,000
Book value of loans receivable	$ 1,200,000		$ 1,200,000		$ 4,200,000
Number of loans repaid | loan			1