Fair Value of Financial Instruments - Schedule of Fair Value Hierarchy (Details) - USD ($) $ in Millions	Sep. 30, 2024		Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 13,943.4	[1],[2]	$ 14,649.3	[3],[4],[5],[6],[7]
Level 1—Price quotations in active markets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1.0		1.0
Level 2—Significant other observable inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	91.0		178.0
Level 3—Significant unobservable inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	12,467.0		13,073.0
Investments measured at net asset value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1,384.0		$ 1,397.0

[1] Security may be an obligation of one or more entities affiliated with the named company

[2] See Note 8 for additional information regarding the fair value of the Company’s financial instruments

[3] Security is classified as Level 1 or 2 in the Company's fair value hierarchy (see Note 8).

[4] Security is non-income producing.

[5] Security or portion thereof is pledged as collateral supporting the amounts outstanding under the Senior Secured Revolving Credit Facility (see Note 9).

[6] Security may be an obligation of one or more entities affiliated with the named company.

[7] Fair value determined by the Company’s board of directors (see Note 8).