Gladstone Capital Corporation Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

BORROWINGS - Revolving Line of Credit Narrative (Details)

BORROWINGS - Revolving Line of Credit Narrative (Details) - Credit Facility - Line of Credit				12 Months Ended
	Jun. 16, 2023 USD ($)	Sep. 12, 2022	May 13, 2022 USD ($)	Sep. 30, 2023 USD ($) obligor	Sep. 30, 2022 USD ($)	Jun. 15, 2023 USD ($)	Oct. 31, 2022 USD ($)	Oct. 30, 2022 USD ($)	Sep. 20, 2022 USD ($)	Sep. 19, 2022 USD ($)	May 12, 2022 USD ($)
Revolving Line of Credit
Debt Instrument [Line Items]
Commitment amount			$ 175,000,000	$ 223,659,000	$ 225,000,000						$ 205,000,000
Unused fee percentage			0.35%	1.00%	0.50%
Average unused fee percentage			35.00%
Debt instrument, fee			$ 1,100,000
Debt instrument, covenant, borrowing base, minimum number of obligors \| obligor				25
Covenant, required minimum net worth of mandatory redeemable term preferred stock				$ 325,000,000
Covenant, required minimum net worth of mandatory redeemable term preferred stock, plus percent of all equity and subordinated debt raised				50.00%
Covenant, required minimum net worth of mandatory redeemable term preferred stock, minus percent of any equity or subordinated debt redeemed or retired				50.00%
Covenant, required minimum net worth of mandatory redeemable term preferred stock, plus percent of all equity and subordinated debt raised, minus percent of any equity or subordinated debt redeemed or retired				$ 408,900,000
Covenant, senior security, indebtedness, required minimum asset coverage ratio				150.00%
Senior security, indebtedness, asset coverage amount				$ 660,500,000
Indebtedness asset coverage on our senior securities				231.10%
Number of obligors \| obligor				37
Revolving Line of Credit \| LIBOR
Debt Instrument [Line Items]
Debt instrument, variable rate floor			0.35%
Revolving Line of Credit \| LIBOR, Tranche One
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			2.70%
Revolving Line of Credit \| LIBOR, Thereafter
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			3.25%
Revolving Line of Credit \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				3.10%	2.81%
Revolving Line of Credit - Amendment No. 1 \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.11%
Revolving Line of Credit - Amendment No. 2
Debt Instrument [Line Items]
Commitment amount									$ 225,000,000	$ 175,000,000
Line of credit facility, increase in borrowing capacity									$ 50,000,000
Revolving Line of Credit - Amendment No. 3
Debt Instrument [Line Items]
Commitment amount							$ 245,000,000	$ 225,000,000
Line of credit facility, increase in borrowing capacity							$ 20,000,000
Revolving Line of Credit - Amendment No. 4
Debt Instrument [Line Items]
Commitment amount	$ 223,700,000					$ 245,000,000
Debt instrument, fee	$ 1,200,000
Revolving Line of Credit - Amendment No. 4 \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.10%
Revolving Line of Credit - Amendment No. 4 \| SOFR, Tranche One
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.00%
Revolving Line of Credit - Amendment No. 4 \| SOFR, Thereafter
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.50%