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The amount of debt that is retained.

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Face (par) amount of debt instrument at time of issuance.

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Debt - 2019-1 Debt (Details) $ in Thousands					3 Months Ended	12 Months Ended
Debt - 2019-1 Debt (Details) $ in Thousands	Jul. 02, 2025 USD ($)	Jun. 15, 2023	Nov. 30, 2021 USD ($)	Aug. 28, 2019 USD ($)	Mar. 31, 2026 USD ($) Loan	Dec. 31, 2025 USD ($) Loan
Debt
Principal amount					$ 2,127,000	$ 2,077,000
Number of investments secured as collateral \| Loan					52	48
Fair value of investments secured as collateral					$ 395,700	$ 380,600
Cash secured as collateral					11,700	26,800
Unamortized debt issuance costs					$ 17,144	10,110
Secured Debt
Debt
Debt instrument percentage of interest retained					100.00%
2019-1 Notes
Debt
Realized gains (losses) on debt securitization				$ 0
Principal amount			$ 410,000	$ 501,000	$ 272,000	272,000
Investment membership interest					102,300
Net realized loss on extinguishment of debt			$ 2,300
Membership interest retained (as a percent)			5.00%
Unamortized debt issuance costs					1,700	$ 1,800
2019-1 Notes \| BCC Middle Market CLO 2019
Debt
Spread rate (as a percent)		0.26%
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]		us-gaap:SecuredOvernightFinancingRateSofrMember
Reset Transaction \| Secured Debt
Debt
Principal amount	$ 430,300
Class A1R senior secured floating rate notes
Debt
Principal amount			$ 282,500
Interest rate (as a percent)			1.50%
Class A2R senior secured floating rate notes
Debt
Principal amount			$ 55,000
Interest rate (as a percent)			2.00%
Class BR senior deferrable floating rate notes
Debt
Principal amount			$ 47,500
Interest rate (as a percent)			2.60%
Debt instrument retained			$ 32,500
Class CR senior deferrable floating rate notes
Debt
Principal amount			$ 25,000
Interest rate (as a percent)			3.75%
Debt instrument retained			$ 25,000
Class A-1-RR Senior Secured Floating Rate Notes \| Secured Debt
Debt
Principal amount	$ 232,000
Spread rate (as a percent)	1.45%
Class A-2-RR Senior Secured Floating Rate Notes \| Secured Debt
Debt
Principal amount	$ 16,000
Spread rate (as a percent)	1.60%
Class A-3-RR Senior Secured Floating Rate \| Secured Debt
Debt
Principal amount	$ 24,000
Interest rate (as a percent)	1.85%
Class B-RR Secured Deferrable Floating Rate Notes \| Secured Debt
Debt
Principal amount	$ 32,000
Debt instrument retained					32,000
Spread rate (as a percent)	2.35%
Class C-RR Secured Deferrable Floating Rate Notes \| Secured Debt
Debt
Principal amount	$ 24,000
Debt instrument retained					$ 24,000
Spread rate (as a percent)	3.35%