XML 55 R44.htm IDEA: XBRL DOCUMENT v3.24.0.1

Fair Value Measurements - Summary of Reconciliation of Beginning and Ending Balances for Fair Valued Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Realized gain on investments	Realized gain on investments
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Realized gain on investments	Realized gain on investments
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net change in unrealized appreciation (depreciation) on investments	$ (12,219)	$ (28,524)
Level 3 | Fair Value, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	860,019	718,767
Net realized gains (losses) on investments	24,071	65,635
Net change in unrealized appreciation (depreciation) on investments	(10,353)	(65,655)
Purchase of investments	336,741	333,846
Proceeds from sales and repayments of investments	(258,828)	(193,980)
Interest and dividend income paid-in-kind	6,634	1,663
Proceeds from loan origination fees	(3,600)	(2,124)
Accretion of loan origination fees	2,504	1,625
Accretion of original issue discount	461	242
Ending Balance	957,649	860,019
Subordinated Debt | Level 3 | Fair Value, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	101,456	36,064
Net realized gains (losses) on investments	178
Net change in unrealized appreciation (depreciation) on investments	(1,096)	753
Purchase of investments	42,041	66,516
Proceeds from sales and repayments of investments	(10,328)	(2,000)
Interest and dividend income paid-in-kind	3,348	415
Proceeds from loan origination fees	(622)	(350)
Accretion of loan origination fees	189	58
Accretion of original issue discount	7
Ending Balance	135,173	101,456
First Lien Debt | Level 3 | Fair Value, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	456,105	354,922
Net realized gains (losses) on investments		(1,717)
Net change in unrealized appreciation (depreciation) on investments	(2,064)	904
Purchase of investments	245,741	189,149
Proceeds from sales and repayments of investments	(122,680)	(87,622)
Interest and dividend income paid-in-kind	1,516	597
Proceeds from loan origination fees	(2,647)	(1,566)
Accretion of loan origination fees	2,101	1,412
Accretion of original issue discount	68	26
Ending Balance	578,140	456,105
Second Lien Debt | Level 3 | Fair Value, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	182,948	158,815
Net realized gains (losses) on investments	(10,168)
Net change in unrealized appreciation (depreciation) on investments	1,461	(20,948)
Purchase of investments	25,000	67,998
Proceeds from sales and repayments of investments	(81,719)	(23,731)
Interest and dividend income paid-in-kind	1,770	651
Proceeds from loan origination fees	(331)	(208)
Accretion of loan origination fees	214	155
Accretion of original issue discount	386	216
Ending Balance	119,561	182,948
Equity | Level 3 | Fair Value, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	117,431	165,762
Net realized gains (losses) on investments	34,061	65,817
Net change in unrealized appreciation (depreciation) on investments	(11,343)	(45,610)
Purchase of investments	23,959	10,183
Proceeds from sales and repayments of investments	(44,101)	(78,721)
Ending Balance	120,007	117,431
Warrant | Level 3 | Fair Value, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	2,079	3,204
Net realized gains (losses) on investments		1,535
Net change in unrealized appreciation (depreciation) on investments	2,689	(754)
Proceeds from sales and repayments of investments		(1,906)
Ending Balance	$ 4,768	$ 2,079

X

- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis asset, accretion of loan origination fees.

+ References

No definition available.

+ Details

Name:	fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfLoanOriginationFees
Namespace Prefix:	fdus_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset, Accretion Of Original Issue Discount

+ References

No definition available.

+ Details

Name:	fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfOriginalIssueDiscount
Namespace Prefix:	fdus_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis asset, interest and dividend income paid-in-kind.

+ References

No definition available.

+ Details

Name:	fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetInterestAndDividendIncomePaidInKind
Namespace Prefix:	fdus_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Fair value measurement with unobservable inputs reconciliation recurring basis asset, proceeds from loan origination fees.

+ References

No definition available.

+ Details

Name:	fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetProceedsFromLoanOriginationFees
Namespace Prefix:	fdus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Indicates line item in statement in which net income is reported that includes unrealized gain (loss) from asset measured at fair value using unobservable input (level 3) and still held.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-SubTopic 10
-Topic 820
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Indicates line item in statement in which net income is reported that includes gain (loss) from asset measured at fair value using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_SubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=fdus_FirstLienDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=fdus_SecondLienDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=fdus_EquityInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_WarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: