REAL ESTATE PROPERTIES HELD FOR INVESTMENT - Narrative (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) Property acquisition Facilitiy	Dec. 31, 2016 USD ($) Facilitiy	Jan. 01, 2018 USD ($)
Real Estate Properties [Line Items]
Earn-out arrangements expired		1
Payout under earn-out arrangement		$ 0
Number of properties transitioned, earn out terminated | Property		8
Payment of contingent consideration	$ 400,000
Decrease in contingent consideration liability		$ 400,000	$ 1,500,000
Weighted average expiration period		9 years
Security deposit liability		$ 20,300,000	2,700,000
Letters of credit deposited		81,100,000	21,300,000
Deposits held for future real estate taxes, insurance expenditures and tenant improvement		28,300,000
Reserve for unpaid cash rents		3,200,000	3,200,000
Reserve associated with straight-line rental income		$ 12,400,000	$ 3,700,000
Genesis Healthcare, Inc.
Real Estate Properties [Line Items]
Number of properties | Facilitiy		54
Number of properties to be sold | Facilitiy		46
Number of properties to be retained | Facilitiy		8
Genesis Healthcare, Inc. | Subsequent Event
Real Estate Properties [Line Items]
Reduction of annual base rent				$ 19,000,000
Minimum
Real Estate Properties [Line Items]
Operating lease expiration period		1 year
Maximum
Real Estate Properties [Line Items]
Operating lease expiration period		15 years
Weighted Average
Real Estate Properties [Line Items]
Operating lease expiration period		9 years
Operating Segments
Real Estate Properties [Line Items]
Number of properties | Facilitiy		507	183
Operating Segments | Senior Housing - Managed
Real Estate Properties [Line Items]
Number of properties | Facilitiy		13	2
Acquisitions With Contingent Consideration Arrangements
Real Estate Properties [Line Items]
Number of real estate acquisitions | acquisition		3
Estimated earn-out value		$ 3,200,000