SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Thousands	Jun. 30, 2020 USD ($) variable_interest_entity Investment	Mar. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Accounting Policies [Line Items]
Number of investments in loans accounted for as real estate joint ventures | Investment	0
Cumulative effect of ASU adoption	$ 3,361,251	$ 3,395,213		$ 3,488,460	$ 3,260,376	$ 3,050,778	$ 3,254,747
Total assets	6,023,553			6,069,299
Cumulative Distributions in Excess of Net Income
Accounting Policies [Line Items]
Cumulative effect of ASU adoption	$ (663,901)	$ (631,251)		(573,283)	$ (460,832)	$ (462,555)	(271,595)
Topic 326
Accounting Policies [Line Items]
Total assets			$ (200)
Primary Beneficiary
Accounting Policies [Line Items]
Number of variable interest entities | variable_interest_entity	0
Cumulative Effect in Period of Adoption
Accounting Policies [Line Items]
Cumulative effect of ASU adoption				(167)			(32,502)
Cumulative Effect in Period of Adoption | Cumulative Distributions in Excess of Net Income
Accounting Policies [Line Items]
Cumulative effect of ASU adoption				$ (167)			$ (32,502)
Cumulative Effect in Period of Adoption | Topic 326 | Cumulative Distributions in Excess of Net Income
Accounting Policies [Line Items]
Cumulative effect of ASU adoption			$ (200)