XML 111 R54.htm IDEA: XBRL DOCUMENT
v3.25.3

BORROWINGS - Revolving Line of Credit Narrative (Details) - Credit Facility - Revolving Line of Credit - Line of Credit $ in Thousands | 12 Months Ended
--- | ---
Sep. 30, 2025 USD ($) obligor | Sep. 30, 2024 USD ($)
Debt Instrument [Line Items] |  |
Line of credit facility, maximum borrowing capacity | $ 320,000 | $ 293,659
Line of credit facility, accordion feature maximum borrowing capacity | $ 400,000 |
Debt instrument, basis spread on variable rate | 2.60% | 3.10%
Debt instrument, covenant, borrowing base, minimum number of obligors | obligor | 25 |
Covenant, required minimum net worth of mandatory redeemable term preferred stock | $ 500,000 |
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 | $ 581,000 |
Debt instrument, covenant, senior security, indebtedness, required minimum asset coverage ratio | 150.00% |
Senior security, indebtedness, asset coverage amount | $ 877,900 |
Indebtedness asset coverage on our senior securities | 219.80% |
Investment company, number of obligor | obligor | 34 |
SOFR, Tranche One |  |
Debt Instrument [Line Items] |  |
Debt instrument, basis spread on variable rate | 2.60% |
SOFR, Thereafter |  |
Debt Instrument [Line Items] |  |
Debt instrument, basis spread on variable rate | 3.10% |

X
- Definition Debt Instrument, Covenant, Borrowing Base, Minimum Number Of Obligors + References No definition available. + Details
Name: | glad_DebtInstrumentCovenantBorrowingBaseMinimumNumberOfObligors
Namespace Prefix: | glad_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Debt Instrument, Covenant, Net Worth Of Mandatory Redeemable Term Preferred Stock, Plus Percent of All Equity and Subordinated Debt Raised, Minus Any Equity Or Subordinated Debt Redeemed or Retired + References No definition available. + Details
Name: | glad_DebtInstrumentCovenantNetWorthOfMandatoryRedeemableTermPreferredStockPlusPercentOfAllEquityAndSubordinatedDebtRaisedMinusAnyEquityOrSubordinatedDebtRedeemedOrRetired
Namespace Prefix: | glad_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock + References No definition available. + Details
Name: | glad_DebtInstrumentCovenantRequiredMinimumNetWorthOfMandatoryRedeemableTermPreferredStock
Namespace Prefix: | glad_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock, Minus Percent of Any Equity Or Subordinated Debt Redeemed Or Retired + References No definition available. + Details
Name: | glad_DebtInstrumentCovenantRequiredMinimumNetWorthOfMandatoryRedeemableTermPreferredStockMinusPercentOfAnyEquityOrSubordinatedDebtRedeemedOrRetired
Namespace Prefix: | glad_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Debt Instrument, Covenant, Required Minimum Net Worth Of Mandatory Redeemable Term Preferred Stock, Plus Percent of All Equity and Subordinated Debt Raised + References No definition available. + Details
Name: | glad_DebtInstrumentCovenantRequiredMinimumNetWorthOfMandatoryRedeemableTermPreferredStockPlusPercentOfAllEquityAndSubordinatedDebtRaised
Namespace Prefix: | glad_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Debt Instrument, Covenant, Senior Security, Indebtedness, Required Minimum Asset Coverage Ratio + References No definition available. + Details
Name: | glad_DebtInstrumentCovenantSeniorSecurityIndebtednessRequiredMinimumAssetCoverageRatio
Namespace Prefix: | glad_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Investment Company, Number of Obligors + References No definition available. + Details
Name: | glad_InvestmentCompanyNumberOfObligors
Namespace Prefix: | glad_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Investment Company, Senior Security, Indebtedness, Asset Coverage Amount + References No definition available. + Details
Name: | glad_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageAmount
Namespace Prefix: | glad_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line Of Credit Facility, Accordion Feature, Maximum Borrowing Capacity + References No definition available. + Details
Name: | glad_LineOfCreditFacilityAccordionFeatureMaximumBorrowingCapacity
Namespace Prefix: | glad_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8A -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 235 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477314/942-235-S99-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480738/235-10-S50-4 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-3 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(f)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 835 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482949/835-30-55-8 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B Reference 9: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69B -Publisher FASB -URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B Reference 10: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69C -Publisher FASB -URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C Reference 11: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69E -Publisher FASB -URI https://asc.fasb.org/1943274/2147481568/470-20-55-69E Reference 12: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 69F -Publisher FASB -URI https://asc.fasb.org/1943274/2147481568/470-20-55-69F Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B Reference 15: http://www.xbrl.org/2003/role/exampleRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (h) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1D -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1D -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1D -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1E -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1E -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1E -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1F -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1F -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1F -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1F -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1I -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1I Reference 30: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 835 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482925/835-30-45-2 Reference 31: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 835 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482900/835-30-50-1 + Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of total assets less all liabilities and indebtedness not represented by senior security, to senior security representing indebtedness. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name Investment Company Act of 1940 -Section 61 -Paragraph a -Subparagraph (1) -Publisher SEC + Details
Name: | us-gaap_InvestmentCompanySeniorSecurityIndebtednessAssetCoverageRatio
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(19)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=glad_RevolvingLineOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VariableRateAxis=glad_SecuredOvernightFinancingRateSOFRTrancheOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VariableRateAxis=glad_SecuredOvernightFinancingRateSOFRThereafterMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |