Debt instrument issued amount.

No definition available.

Name:	fdus_DebtInstrumentIssuedAmount
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Period Type:	instant

- Definition

Nonaccrual status debt recovered.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

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Period Type:	instant

- Definition

Date the declared dividend will be paid, in YYYY-MM-DD format.

+ References

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-Name Accounting Standards Codification
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+ Details

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Period Type:	duration

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

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Balance Type:	na
Period Type:	instant

- Definition

Date the holder must own the stock to be entitled to the dividend, in YYYY-MM-DD format.

+ References

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- Definition

Indicates type of investment. Includes, but is not limited to, common stock, preferred stock, convertible security, fixed income security, government security, option purchased, warrant, loan participation and assignment, commercial paper, bankers' acceptance, certificates of deposit, short-term security, repurchase agreement, and other investment company.

+ References

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- Definition

Amount, before tax, of realized gain (loss) on investment and derivative, classified as operating. Investment includes, but is not limited to, debt and equity securities, security sold short, real estate, and commodity.

+ References

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+ Details

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- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

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- Details

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- Details

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- Details

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- Details

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- Details

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Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended		6 Months Ended
	Aug. 03, 2026	Jul. 31, 2026	Aug. 04, 2025	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Jul. 24, 2026	Dec. 31, 2025
Subsequent Event [Line Items]
Aggregate realized loss				$ 6,425	$ (7,568)	$ (5,780)	$ 5,762
Investment, Type [Extensible Enumeration]				Pfanstiehl Inc [Member]		Pfanstiehl Inc [Member]			Pfanstiehl Inc [Member]
Regular Dividends
Subsequent Event [Line Items]
Dividends to stockholders			$ 0.43
Dividend payable date			Sep. 25, 2025
Dividend record date			Sep. 18, 2025
Regular Dividends \| Subsequent Events
Subsequent Event [Line Items]
Dividends to stockholders	$ 0.43
Supplemental Dividends
Subsequent Event [Line Items]
Dividends to stockholders			$ 0.14
Dividend payable date			Sep. 25, 2025
Dividend record date			Sep. 18, 2025
Supplemental Dividends \| Subsequent Events
Subsequent Event [Line Items]
Dividends to stockholders	$ 0.07
Quarterly Dividends \| Subsequent Events
Subsequent Event [Line Items]
Dividend payable date	Sep. 29, 2026
Dividend record date	Sep. 15, 2026
SBA Debentures \| 4.746% Fixed Interest Rate \| Subsequent Events
Subsequent Event [Line Items]
Debt instrument issued amount								$ 7,500
Interest rate								4.746%
Second Lien and Subordinated Debt \| Subsequent Events \| Virtex Enterprises, LP
Subsequent Event [Line Items]
Aggregate realized loss		$ 10,995
Nonaccrual status debt recovered		$ 204