INVESTMENTS - Ivy Hill Asset Management, L.P. (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) borrower	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) borrower	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Schedule of Investments [Line Items]
Amortized cost of investments	$ 21,685.6		$ 21,685.6		$ 22,043.0
Purchases of investments			2,452.0	$ 4,849.0
Ivy Hill Asset Management, L.P.
Schedule of Investments [Line Items]
Amortized cost of investments	1,968.0		1,968.0		2,048.0
Purchases of investments			7.0	27.0
Realized loss on sale of investments			11.0	7.0
Ivy Hill Asset Management, L.P.
Schedule of Investments [Line Items]
Assets under management	$ 13,500.0		$ 13,500.0
Number of borrowers | borrower	22		22
Amortized cost of investments	$ 2,436.0		$ 2,436.0		$ 2,370.0
Management and incentive fee income	13.0	$ 12.0	27.0	21.0
Other investment-related income	$ 95.0	$ 44.0	156.0	79.0
Purchases of investments			$ 691.0	$ 1,555.0