LOANS RECEIVABLE AND OTHER INVESTMENTS - Narrative (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) Investment loan	Dec. 31, 2016 USD ($) loan	Aug. 17, 2017 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | Investment	22
Book value of loans	$ 91,280,000
Outstanding principal balance	66,004,000	$ 53,596,000
Loan loss reserve	$ 97,000	$ 2,750,000
Nonperforming Financial Instruments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan	0	3
Outstanding principal balance		$ 17,400,000
Provision for loan losses	$ 4,800,000	$ 3,100,000
Number of loans on which provision for losses were recorded | loan	2	4
Number of loans on nonaccrual status | loan	1
Value of loans on nonaccrual status	$ 0
Number of loans partially repaid prior to year end with on which provision for losses were recorded | loan		1
Portfolio-Based Loan Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Decrease in provision	300,000	$ 1,300,000
Loan loss reserve	100,000	400,000
Specific Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan loss reserve	0	$ 2,300,000
Care Capital Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan			18
Book value of loans			$ 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 | loan			8
Book value of loans			$ 36,300,000
Fair value of loans receivable			11,300,000
Accretable yield	2,700,000		$ 2,900,000
Accretion recorded in interest and other income	200,000
Outstanding principal balance	$ 10,000,000