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Line Of Credit Facility, Prepayment Fee, Second Year After Effective Date, Percentage

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Borrowings - GBDC 3 DB Credit Facility (Details) - USD ($) $ in Thousands	6 Months Ended
	Nov. 18, 2024	Jun. 30, 2025	Sep. 30, 2024
Debt Instrument [Line Items]
Long-term debt		$ 5,127,148	$ 4,599,430
Revolving Credit Facility \| GBDC 3 DB Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 625,000
Line of credit facility, commitment fee percentage	0.06944%
Line of credit facility, non-usage fee, percentage	0.25%
Line of credit facility, prepayment fee, first year after effective date, percentage	0.50%
Line of credit facility, prepayment fee, second year after effective date, percentage	0.25%
Long-term debt			$ 411,489
Revolving Credit Facility \| GBDC 3 DB Credit Facility \| Line of Credit \| Base Rate
Debt Instrument [Line Items]
Line of credit facility, interest rate during period	2.30%
Line of credit facility, interest rate at period end	2.80%
Revolving Credit Facility \| GBDC 3 DB Credit Facility \| Line of Credit \| Canadian Overnight Repo Rate Average
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.32138%