SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) Property variable_interest_entity Segment Investment	Dec. 31, 2016 USD ($) Investment	Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Line Items]
Number of investments in loans accounted for as real estate joint ventures | Investment	0	0
Acquisition costs capitalized	$ 1,000,000	$ 300,000
Merger and acquisition costs	$ 30,255,000	1,197,000	$ 7,023,000
Extension period for tenant relationship intangible assets	10 years
Impairment losses on real estate investments	$ 1,326,000	29,811,000	$ 0
Assets held for sale	0	0
Restricted cash	68,817,000	9,002,000
Restricted cash held by exchange accommodation titleholder	$ 57,500,000
Number of reportable segments | Segment	1
Restricted Cash Obligations
Property, Plant and Equipment [Line Items]
Restricted cash	$ 6,500,000	6,800,000
Forest Park - Frisco
Property, Plant and Equipment [Line Items]
Impairment losses on real estate investments		$ 29,800,000
Land Improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Land Improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	40 years
Buildings and Building Improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Buildings and Building Improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	40 years
Furniture and Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	1 year
Furniture and Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	20 years
Skilled Nursing/Transitional Care
Property, Plant and Equipment [Line Items]
Impairment losses on real estate investments	$ 1,300,000
Net investment in direct financing lease	$ 23,000,000
Properties in direct financing lease | Property	1
Undiscounted rental payments	$ 7,100,000
Estimated unguaranteed residual value	24,700,000
Unearned lease income	8,800,000
Income from direct financing lease	1,000,000
Future minimum lease payments due 2018	2,200,000
Future minimum lease payments due 2019	2,200,000
Future minimum lease payments due 2020	2,300,000
Future minimum lease payments due 2021	$ 2,100,000
Primary Beneficiary
Property, Plant and Equipment [Line Items]
Number of variable interest entities | variable_interest_entity	19
Primary Beneficiary | Skilled Nursing/Transitional Care
Property, Plant and Equipment [Line Items]
Number of variable interest entities | variable_interest_entity	1
Primary Beneficiary | Exchange Accommodation Titleholder
Property, Plant and Equipment [Line Items]
Number of variable interest entities | variable_interest_entity	18