Prospect Capital InterNotes® - Narrative (Details) - USD ($)	3 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Feb. 13, 2020
Debt Instrument [Line Items]
Loss on extinguishment of debt	$ 28,000	$ 5,357,000
Prospect Capital InterNotes
Debt Instrument [Line Items]
Issuance of debt	2,624,000	87,657,000
Repayments of unsecured debt	1,144,000	214,204,000
Unsecured Debt \| Prospect Capital InterNotes
Debt Instrument [Line Items]
Issuance of debt	2,624,000	87,657,000
Net proceeds of issuance of debt	$ 2,591,000	$ 85,472,000
Weighted average interest rate	4.50%	3.35%
Repurchase amount		$ 213,533,000
Weighted average interest rate over time		5.10%
Loss on extinguishment of debt	$ 35,000	$ 3,719,000
Interest expense	3,683,000	5,302,000
Unsecured Debt \| Prospect Capital InterNotes \| Survivor’s Option
Debt Instrument [Line Items]
Repayments of unsecured debt	$ 1,144,000	$ 671,000
Unsecured Debt \| Prospect Capital InterNotes \| Minimum
Debt Instrument [Line Items]
Stated rate	4.50%	2.25%
Unsecured Debt \| Prospect Capital InterNotes \| Maximum
Debt Instrument [Line Items]
Face amount			$ 1,000,000,000
Stated rate		4.00%

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Fair value amount of debt instrument that was repurchased.

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Weighted average interest rate of debt outstanding.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Weighted average interest rate of long-term debt outstanding calculated over time.

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The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

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