Investment Portfolio - Operations Information for COPJV (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investment Company, Nonconsolidated Subsidiary [Line Items]
Total investment income		$ 407.0	$ 441.0	$ 439.0	$ 434.0	$ 447.0	$ 465.0	$ 462.0	$ 456.0	$ 1,721.0	$ 1,830.0	$ 1,635.0
Expenses
Interest expense	[1]									465.0	467.0	365.0
Professional services										10.0	12.0	15.0
Net expenses										885.0	916.0	751.0
Net investment income										836.0	914.0	$ 884.0
Credit Opportunities Partners JV, LLC
Investment Company, Nonconsolidated Subsidiary [Line Items]
Total investment income										349.2	380.8
Expenses
Interest expense										120.9	123.5
Custodian and accounting fees										1.6	1.6
Administrative services										9.3	9.3
Professional services										0.6	0.6
Other										1.0	1.1
Net expenses										133.4	136.1
Net investment income										215.8	244.7
Net realized and unrealized losses										(22.1)	(30.6)
Net increase in net assets resulting from operations										$ 193.7	$ 214.1

[1] See Note 9 for a discussion of the Company’s financing arrangements.