Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Changes in Level 3 Portfolio (Details)

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Fair Value Measurements - Changes in Level 3 Portfolio (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ 8,028,268 $ 4,895,099
Purchases of investments 1,325,494 862,359
Proceeds from principal repayments and sales of investments (681,112) (30,633)
Transfers into Level 3 0 9,463
Transfers out of Level 3 (6,974) (4,714)
Ending balance 8,697,747 5,796,765
Net change in unrealized appreciation (depreciation) related to financial instruments still held 20,997 56,844
Investments | Accretion (Amortization) of Discounts and Premiums, Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 24,078 8,023
Investments | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (6,806) (1,246)
Investments | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 14,799 58,414
First lien debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 7,956,235 4,882,393
Purchases of investments 1,257,653 861,403
Proceeds from principal repayments and sales of investments (680,727) (30,581)
Transfers into Level 3 0 0
Transfers out of Level 3 (6,974) (4,714)
Ending balance 8,557,580 5,774,333
Net change in unrealized appreciation (depreciation) related to financial instruments still held 20,387 57,176
First lien debt | Accretion (Amortization) of Discounts and Premiums, Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 24,017 7,981
First lien debt | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (6,866) (893)
First lien debt | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 14,242 58,744
Second lien debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 19,441 8,794
Purchases of investments 0 0
Proceeds from principal repayments and sales of investments 0 0
Transfers into Level 3 0 9,463
Transfers out of Level 3 0 0
Ending balance 19,764 18,048
Net change in unrealized appreciation (depreciation) related to financial instruments still held 284 (242)
Second lien debt | Accretion (Amortization) of Discounts and Premiums, Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 39 33
Second lien debt | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 0
Second lien debt | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 284 (242)
Other secured debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 0  
Purchases of investments 63,700  
Proceeds from principal repayments and sales of investments 0  
Transfers into Level 3 0  
Transfers out of Level 3 0  
Ending balance 63,719  
Net change in unrealized appreciation (depreciation) related to financial instruments still held (1)  
Other secured debt | Accretion (Amortization) of Discounts and Premiums, Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 20  
Other secured debt | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0  
Other secured debt | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings (1)  
Unsecured debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 15,936 1,606
Purchases of investments 594 377
Proceeds from principal repayments and sales of investments 0 0
Transfers into Level 3 0 0
Transfers out of Level 3 0 0
Ending balance 16,603 1,915
Net change in unrealized appreciation (depreciation) related to financial instruments still held 71 (79)
Unsecured debt | Accretion (Amortization) of Discounts and Premiums, Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 2 9
Unsecured debt | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 0
Unsecured debt | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 71 (77)
Equity investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 36,656 2,306
Purchases of investments 3,547 579
Proceeds from principal repayments and sales of investments (385) (52)
Transfers into Level 3 0 0
Transfers out of Level 3 0 0
Ending balance 40,081 2,469
Net change in unrealized appreciation (depreciation) related to financial instruments still held 256 (11)
Equity investments | Accretion (Amortization) of Discounts and Premiums, Investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 0 0
Equity investments | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings 60 (353)
Equity investments | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain (loss) included in earnings $ 203 $ (11)