v3.25.2
Borrowings - GBDC 3 2021 Debt Securitization (Narrative) (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Jun. 03, 2024
USD ($)
Jun. 30, 2025
USD ($)
Dec. 31, 2024
USD ($)
Jun. 30, 2024
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Sep. 30, 2024
USD ($)
portfolioCompany
Debt Instrument [Line Items]              
Realized loss on extinguishment of debt   $ 0   $ 0 $ 48 $ 0  
Investments, at fair value   $ 8,961,549 [1]     $ 8,961,549 [1]   $ 8,235,411 [2]
GBDC 3 2021 Debt Securitization              
Debt Instrument [Line Items]              
Debt instrument, face amount $ 398,850            
Debt instrument, basis spread on variable rate         0.26161%    
Realized loss on extinguishment of debt     $ 48        
Number of investment portfolio company | portfolioCompany             81
Investments, at fair value             $ 395,682
GBDC 3 2021 Debt Securitization | Subordinated debt              
Debt Instrument [Line Items]              
Debt instrument, face amount 100,850            
GBDC 3 2021 Debt Securitization | AAA Class A 2021 Notes              
Debt Instrument [Line Items]              
Debt instrument, face amount $ 224,000            
Debt instrument, basis spread on variable rate 1.60%            
GBDC 3 2021 Debt Securitization | AA Class B 2021 Notes              
Debt Instrument [Line Items]              
Debt instrument, face amount $ 28,000            
Debt instrument, basis spread on variable rate 1.85%            
GBDC 3 2021 Debt Securitization | A Class C-1 2021 Notes              
Debt Instrument [Line Items]              
Debt instrument, face amount $ 36,000            
Debt instrument, basis spread on variable rate 2.80%            
GBDC 3 2021 Debt Securitization | A Class C-2 2021 Notes              
Debt Instrument [Line Items]              
Debt instrument, face amount $ 10,000            
Interest rate 3.91%            
GBDC 3 2021 Debt Securitization | BBB Class D 2021 Notes              
Debt Instrument [Line Items]              
Debt instrument, face amount $ 28,000            
GBDC 3 2021 Debt Securitization | Secured 2021 Notes | Maximum              
Debt Instrument [Line Items]              
Debt instrument, basis spread on variable rate 5.00%            
[1] The fair values of investments were valued using significant unobservable inputs, unless noted otherwise. See Note 6.
[2] The fair values of investments were valued using significant unobservable inputs, unless noted otherwise. See Note 6.