LOANS RECEIVABLE AND OTHER INVESTMENTS - Narrative (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) loan preferred_equity_investment	Mar. 31, 2017 USD ($) loan	Dec. 31, 2017 USD ($) loan	Aug. 17, 2017 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans receivable instruments acquired | loan	21
Principal balance	$ 76,212,000
Loan loss reserve	200,000		$ 97,000
Portfolio-Based Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in portfolio-based loan loss reserve	100,000	$ (200,000)
Loan loss reserve	200,000		100,000
Specific Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan loss reserve	0		$ 0
Nonperforming Financial Instruments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan loss reserve in period	$ 0	$ 1,500,000
Number of loans receivable on nonaccrual status | loan	1		1
Book value of loans receivable on nonaccrual status	$ 0		$ 0
Number of preferred equity investments on nonaccrual status | preferred_equity_investment	3
Book value of preferred equity investments on nonaccrual status	$ 14,300,000
Number of loans on which provision for losses were recorded | loan		3
Care Capital Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans receivable instruments acquired | loan				18
Principal balance				$ 83,300,000
Fair value of loans receivable				$ 58,200,000
Care Capital Properties | Receivables Acquired with Deteriorated Credit Quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans receivable instruments acquired | loan				8
Principal balance				$ 36,300,000
Fair value of loans receivable				11,300,000
Accretable yield	2,000,000		2,600,000	$ 3,500,000
Interest payments received	500,000
Accretion recorded in interest and other income	100,000
Book value of loans receivable	$ 9,600,000		$ 10,000,000