SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Other Income (Expense), Net) (Details) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Income tax benefit related to Tax Act, tax receivable liability	$ 145.1	$ 145.1
Oaktree Capital Group Excluding Consolidated Funds \| $250,000, 6.75%, issued in November 2009, payable on December 2, 2019
Debt Instrument [Line Items]
Make-whole premium expense related to early repayment of debt		22.0
Debt redeemed		$ 250.0
Stated rate	6.75%	6.75%

Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Income Tax Receivables, Income Tax Expense (Benefit)

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