v3.25.0.1
Borrowings - GBDC 3 2021 Debt Securitization (Narrative) (Details)
$ in Thousands
3 Months Ended
Jun. 03, 2024
USD ($)
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Sep. 30, 2024
USD ($)
portfolioCompany
Debt Instrument [Line Items]        
Realized loss on extinguishment of debt   $ 48 $ 0  
Investments, at fair value   $ 8,685,231 [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. Fair Value Measurements”.
[2] The fair values of investments were valued using significant unobservable inputs, unless noted otherwise. See “Note 6. Fair Value Measurements”.