v3.26.1
Fair Value of Financial Instruments - Schedule of Investments at Amortized Cost and Fair Value (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments at Amortized Cost $ 4,146,165 [1],[2],[3] $ 4,178,354 [4],[5],[6]
Investments at Fair Value $ 4,050,457 [1],[2],[3] $ 4,071,008 [4],[5],[6]
Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value Percentage of Total Portfolio 100.00% 100.00%
Senior Secured First Lien Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments at Amortized Cost $ 3,137,571 $ 3,215,223
Investments at Fair Value $ 3,066,779 $ 3,136,374
Senior Secured First Lien Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value Percentage of Total Portfolio 75.70% 77.10%
Senior Secured Second Lien Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments at Amortized Cost $ 175,601 $ 160,045
Investments at Fair Value $ 165,459 $ 152,406
Senior Secured Second Lien Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value Percentage of Total Portfolio 4.10% 3.70%
Subordinated Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments at Amortized Cost $ 292,873 $ 264,813
Investments at Fair Value $ 285,017 $ 259,132
Subordinated Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value Percentage of Total Portfolio 7.00% 6.40%
Collateralized Securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments at Amortized Cost $ 7,649 $ 7,642
Investments at Fair Value $ 4,098 $ 4,861
Collateralized Securities | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value Percentage of Total Portfolio 0.10% 0.10%
Equity/Other    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments at Amortized Cost $ 307,310 $ 305,470
Investments at Fair Value $ 306,398 $ 293,279
Equity/Other | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value Percentage of Total Portfolio 7.60% 7.20%
FBLC Senior Loan Fund, LLC    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments at Amortized Cost $ 225,161 $ 225,161
Investments at Fair Value $ 222,706 $ 224,956
FBLC Senior Loan Fund, LLC | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value Percentage of Total Portfolio 5.50% 5.50%
[1] Percentages are based on net assets attributable to common stock as of March 31, 2026.
[2] Unless otherwise indicated, all investments in the consolidated schedules of investments are non-affiliated, non-controlled investments.
[3] Unless otherwise indicated, all of the Company's investments or a portion thereof are pledged as collateral under the JPM Revolver Facility.
[4] Percentages are based on net assets attributable to common stock as of December 31, 2025.
[5] Unless otherwise indicated, all investments in the consolidated schedules of investments are non-affiliated, non-controlled investments.
[6] Unless otherwise indicated, all of the Company's investments or a portion thereof are pledged as collateral under the JPM Revolver Facility (as defined below).