SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) Property variable_interest_entity Segment Investment loan	Dec. 31, 2014 USD ($) Property Investment	Dec. 31, 2013 USD ($) Property
Property, Plant and Equipment [Line Items]
Number of entities in which company is primary beneficiary | variable_interest_entity	2
Number of investments in loans accounted for as real estate joint ventures | Investment	0	0
Number of real estate properties acquired | Property	24	42	2
Acquisition pursuit costs	$ 7,000,000	$ 3,100,000	$ 1,500,000
Impairment losses on real estate investments	0	0	$ 0
Assets held for sale	$ 0	0
Number of loan receivable investment | loan	17
Principal balance	$ 273,811,000
Loan loss reserve	4,300,000	0
Restricted cash	9,813,000	7,024,000
Deferred financing costs, net of amortization	$ 22,000,000	25,800,000
Number of reportable segments | Segment	1
Cash Obligations [Member]
Property, Plant and Equipment [Line Items]
Restricted cash	$ 5,000,000	$ 4,900,000
Loan Receivable Investment [Member]
Property, Plant and Equipment [Line Items]
Number of loan receivable investment | Investment	1
Principal balance	$ 13,400,000
Loan loss reserve	2,500,000
Portfolio-Based Loan [Member]
Property, Plant and Equipment [Line Items]
Loan loss reserve	$ 1,800,000
Loans on Nonaccrual Status [Member]
Property, Plant and Equipment [Line Items]
Number of loan receivable investment | Investment	2	0
Loan receivable on nonaccrual status	$ 123,500,000
Loans on Accrual Status [Member] | Over 90 Days Past Due [Member]
Property, Plant and Equipment [Line Items]
Number of loan receivable investment | Investment	1
Loan receivable, past due	$ 60,900,000
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	40 years
Buildings and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Buildings and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	40 years
Furniture and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	1 year
Furniture and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	20 years