SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Energy Investments held by KKR (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2020
Additional Paid-In Capital
Class of Stock [Line Items]
Transfer of oil and gas interests	$ (45,669)	$ (45,669)
Noncontrolling Interests
Class of Stock [Line Items]
Noncontrolling interest, transfer of oil and gas interests	$ 23,358	$ 23,358

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