FAIR VALUE OF FINANCIAL INSTRUMENTS - Schedule of Fair Value Measurement Inputs and Valuation Techniques (Details) $ in Millions	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	$ 21,779.8	$ 20,009.5
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	21,361.0	19,908.0
Level 3 | Yield analysis | First lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	9,165.0	9,456.0
Level 3 | Yield analysis | Second lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	3,841.0	4,432.0
Level 3 | Yield analysis | Senior subordinated loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	1,021.0	889.0
Level 3 | Discounted cash flow analysis | Subordinated certificates of the SDLP
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	1,249.0	987.0
Level 3 | Discounted cash flow analysis | Ivy Hill Asset Management, L.P.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	2,201.0	936.0
Level 3 | EV market multiple analysis | Preferred equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	2,023.0	1,561.0
Level 3 | EV market multiple analysis | Other equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value	$ 1,861.0	$ 1,647.0
Level 3 | Market yield | Yield analysis | Minimum | First lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	7.6	2
Level 3 | Market yield | Yield analysis | Minimum | Second lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	11	6.8
Level 3 | Market yield | Yield analysis | Minimum | Senior subordinated loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	8	7.1
Level 3 | Market yield | Yield analysis | Maximum | First lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	26.1	16.5
Level 3 | Market yield | Yield analysis | Maximum | Second lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	32.4	22.9
Level 3 | Market yield | Yield analysis | Maximum | Senior subordinated loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	16.3	27.8
Level 3 | Market yield | Yield analysis | Weighted Average | First lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	12.3	7.6
Level 3 | Market yield | Yield analysis | Weighted Average | Second lien senior secured loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	14.9	9.5
Level 3 | Market yield | Yield analysis | Weighted Average | Senior subordinated loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	12.9	11.5
Level 3 | Discount rate | Discounted cash flow analysis | Minimum | Subordinated certificates of the SDLP
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	12.4	8.8
Level 3 | Discount rate | Discounted cash flow analysis | Minimum | Ivy Hill Asset Management, L.P.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	12.9	9.9
Level 3 | Discount rate | Discounted cash flow analysis | Maximum | Subordinated certificates of the SDLP
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	14.8	9.7
Level 3 | Discount rate | Discounted cash flow analysis | Maximum | Ivy Hill Asset Management, L.P.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	25.7	27.9
Level 3 | Discount rate | Discounted cash flow analysis | Weighted Average | Subordinated certificates of the SDLP
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	13.5	9.3
Level 3 | Discount rate | Discounted cash flow analysis | Weighted Average | Ivy Hill Asset Management, L.P.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	14.2	16.3
Level 3 | EBITDA multiple | EV market multiple analysis | Minimum | Preferred equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	2.6	3.2
Level 3 | EBITDA multiple | EV market multiple analysis | Minimum | Other equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	2.1	4.9
Level 3 | EBITDA multiple | EV market multiple analysis | Maximum | Preferred equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	40.6	64.4
Level 3 | EBITDA multiple | EV market multiple analysis | Maximum | Other equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	52.1	32.1
Level 3 | EBITDA multiple | EV market multiple analysis | Weighted Average | Preferred equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	15.7	16.5
Level 3 | EBITDA multiple | EV market multiple analysis | Weighted Average | Other equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Input	15.6	14.9