Investments - Fair Value and Amortized Cost (Details) - USD ($) $ in Thousands	Sep. 30, 2025		Jun. 30, 2025	Dec. 31, 2024		Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Amortized Cost	$ 3,906,977	[1],[2],[3]		$ 3,159,171	[4],[5],[6]
Fair Value	3,900,686	[2],[3]		3,161,223	[5],[6]
Non-controlled/non-affiliated
Schedule of Investments [Line Items]
Amortized Cost	3,821,388	[1]		3,084,619	[4]
Fair Value	3,804,018			3,080,569
Non-controlled/affiliated
Schedule of Investments [Line Items]
Amortized Cost	85,589	[1]		74,552	[4]
Fair Value	96,668		$ 91,868	80,654		$ 78,081	$ 69,913	$ 54,714
First lien senior secured debt | Non-controlled/non-affiliated
Schedule of Investments [Line Items]
Amortized Cost	3,820,975			3,084,605
Fair Value	3,804,000			3,080,554
Sponsor subordinated note | Non-controlled/non-affiliated
Schedule of Investments [Line Items]
Amortized Cost	413			14
Fair Value	$ 18			$ 15

[1] The amortized cost represents the original cost adjusted for the amortization of discounts and premiums, as applicable, on debt investments using the effective interest method.

[2] Unless otherwise indicated, all investments represent co-investments made with the Company’s affiliates in accordance with the terms of the exemptive relief that the Company received from the U.S. Securities and Exchange Commission. Refer to Note 6 for further information.

[3] Unless otherwise indicated, all investments are considered Level 3 investments.

[4] The amortized cost represents the original cost adjusted for the amortization of discounts and premiums, as applicable, on debt investments using the effective interest method.

[5] Unless otherwise indicated, all investments represent co-investments made with the Company’s affiliates in accordance with the terms of the exemptive relief that the Company received from the U.S. Securities and Exchange Commission. Refer to Note 6 for further information.

[6] Unless otherwise indicated, all investments are considered Level 3 investments.