v3.26.1
Borrowings - GBDC 3 2021 Debt Securitization - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Jun. 03, 2024
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2024
Jun. 30, 2026
Jun. 30, 2025
Debt Instrument [Line Items]            
Realized loss on extinguishment of debt   $ 0 $ 0   $ 0 $ 48
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    
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%