XML 245 R44.htm IDEA: XBRL DOCUMENT
v3.25.1

INVESTMENTS - Narrative (Details) $ in Thousands | 1 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 USD ($) state industry portfolioCompany | Feb. 28, 2025 USD ($) | Dec. 31, 2024 USD ($) | Nov. 30, 2024 USD ($) | Sep. 30, 2024 USD ($) | Jul. 31, 2024 USD ($) | May 31, 2024 USD ($) | Mar. 31, 2025 USD ($) state industry portfolioCompany | Mar. 31, 2024 USD ($) | Mar. 31, 2023 USD ($)
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal repayments of investments |  |  |  |  |  |  |  |  |  | $ 123,600 |  | $ 28,000 |  | $ 52,300
Purchase of investments |  |  |  |  |  |  |  |  |  | 221,217 |  | 183,924 |  | 133,756
Success fee income: |  |  |  |  |  |  |  |  |  | 6,770 |  | 3,605 |  | $ 10,402
Cost |  | $ 939,066 | [1] |  |  |  |  |  |  | 939,066 | [1] | 854,290 | [2] |
Fair Value |  | $ 979,320 | [1] |  |  |  |  |  |  | $ 979,320 | [1] | 920,504 | [2] |
Number of investment portfolio company | portfolioCompany |  | 25 |  |  |  |  |  |  |  | 25 |  |  |  |
Number of states which have invested in the company location | state |  | 19 |  |  |  |  |  |  |  | 19 |  |  |  |
Number of industries that have made investments | industry |  | 16 |  |  |  |  |  |  |  | 16 |  |  |  |
Uncollectible receivables allowance, minimum required day for uncollectible adjustment |  |  |  |  |  |  |  |  |  | 90 days |  |  |  |
Gross receivables from portfolio companies |  | $ 2,300 |  |  |  |  |  |  |  | $ 2,300 |  | 2,200 |  |
Allowance for uncollectible receivables |  | 1,700 |  |  |  |  |  |  |  | 1,700 |  | 1,400 |  |
Five Largest Portfolio Investments | Investment Portfolio Benchmark | Customer Concentration Risk |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value |  | 401,700 |  |  |  |  |  |  |  | $ 401,700 |  |  |  |
Percentage of Total Investments |  |  |  |  |  |  |  |  |  | 41.00% |  |  |  |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc. – Common Stock Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 0 | [3],[4],[5] |  |  |  |  |  |  | $ 0 | [3],[4],[5] | 0 | [6],[7],[8] |
Fair Value |  | 0 | [3],[4],[5] |  |  |  |  |  |  | 0 | [3],[4],[5] | 0 | [6],[7],[8] |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc. – Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [6],[8] |  |  |  |  |  |  |  |  |  |  | 3,080 |  |
Fair Value | [6],[8] |  |  |  |  |  |  |  |  |  |  | 3,080 |  |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc. – Line of Credit 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[5],[9] | 3,080 |  |  |  |  |  |  |  | 3,080 |  |  |  |
Fair Value | [3],[5],[9] | 3,080 |  |  |  |  |  |  |  | 3,080 |  |  |  |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc. – Line of Credit 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 930 | [3],[5],[9] |  |  |  |  |  |  | 930 | [3],[5],[9] | 656 | [6],[8] |
Fair Value |  | 930 | [3],[5],[9] |  |  |  |  |  |  | 930 | [3],[5],[9] | 656 | [6],[8] |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[4],[5] | 4,722 |  |  |  |  |  |  |  | 4,722 |  |  |  |
Fair Value | [3],[4],[5] | 0 |  |  |  |  |  |  |  | 0 |  |  |  |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [6],[8] |  |  |  |  |  |  |  |  |  |  | 14,000 |  |
Fair Value | [6],[8] |  |  |  |  |  |  |  |  |  |  | 5,266 |  |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc. – Term Debt 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[5],[9] | 14,000 |  |  |  |  |  |  |  | 14,000 |  |  |  |
Fair Value | [3],[5],[9] | 3,575 |  |  |  |  |  |  |  | 3,575 |  |  |  |
Investment, Identifier [Axis]: B+T Group Acquisition, Inc.– Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [6],[7],[8] |  |  |  |  |  |  |  |  |  |  | 4,722 |  |
Fair Value | [6],[7],[8] |  |  |  |  |  |  |  |  |  |  | 0 |  |
Investment, Identifier [Axis]: Brunswick Bowling Products, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 6,653 | [4],[5] |  |  |  |  |  |  | 6,653 | [4],[5] | 6,653 | [7],[8] |
Fair Value |  | 51,877 | [4],[5] |  |  |  |  |  |  | 51,877 | [4],[5] | 48,759 | [7],[8] |
Investment, Identifier [Axis]: Brunswick Bowling Products, Inc. – Term Debt 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 17,700 | [5] |  |  |  |  |  |  | 17,700 | [5] | 17,700 | [8] |
Fair Value |  | 17,700 | [5] |  |  |  |  |  |  | 17,700 | [5] | 17,700 | [8] |
Investment, Identifier [Axis]: Brunswick Bowling Products, Inc. – Term Debt 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 6,850 | [5] |  |  |  |  |  |  | 6,850 | [5] | 6,850 | [8] |
Fair Value |  | 6,850 | [5] |  |  |  |  |  |  | 6,850 | [5] | 6,850 | [8] |
Investment, Identifier [Axis]: Dema/Mai Holdings, Inc. - Preferred Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [4],[5] | 21,000 |  |  |  |  |  |  |  | 21,000 |  |  |  |
Fair Value | [4],[5] | 31,070 |  |  |  |  |  |  |  | 31,070 |  |  |  |
Investment, Identifier [Axis]: Dema/Mai Holdings, Inc. – Preferred Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [7],[8] |  |  |  |  |  |  |  |  |  |  | 21,000 |  |
Fair Value | [7],[8] |  |  |  |  |  |  |  |  |  |  | 22,181 |  |
Investment, Identifier [Axis]: Dema/Mai Holdings, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 38,250 | [5] |  |  |  |  |  |  | 38,250 | [5] | 38,250 | [8] |
Fair Value |  | 38,250 | [5] |  |  |  |  |  |  | 38,250 | [5] | 38,250 | [8] |
Investment, Identifier [Axis]: Diligent Delivery Systems – Common Stock Warrants |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 500 | [4],[5] |  |  |  |  |  |  | 500 | [4],[5] | 500 | [7],[10] |
Fair Value |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 500 | [7],[10] |
Investment, Identifier [Axis]: Diligent Delivery Systems – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 13,000 | [9],[11] |  |  |  |  |  |  | 13,000 | [9],[11] | 13,000 | [10] |
Fair Value |  | 12,624 | [9],[11] |  |  |  |  |  |  | 12,624 | [9],[11] | 13,000 | [10] |
Investment, Identifier [Axis]: Edge Adhesives Holdings, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 8,199 | [3],[4],[5] |  |  |  |  |  |  | 8,199 | [3],[4],[5] | 8,199 | [6],[7],[8] |
Fair Value |  | 0 | [3],[4],[5] |  |  |  |  |  |  | 0 | [3],[4],[5] | 0 | [6],[7],[8] |
Investment, Identifier [Axis]: Edge Adhesives Holdings, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[5],[9] | 9,210 |  |  |  |  |  |  |  | 9,210 |  |  |  |
Fair Value | [3],[5],[9] | 343 |  |  |  |  |  |  |  | 343 |  |  |  |
Investment, Identifier [Axis]: Edge Adhesives Holdings, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [6],[8],[12] |  |  |  |  |  |  |  |  |  |  | 9,210 |  |
Fair Value | [6],[8],[12] |  |  |  |  |  |  |  |  |  |  | 2,905 |  |
Investment, Identifier [Axis]: Educators Resource, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 8,560 | [4],[5] |  |  |  |  |  |  | 8,560 | [4],[5] | 8,560 | [7],[8] |
Fair Value |  | 21,501 | [4],[5] |  |  |  |  |  |  | 21,501 | [4],[5] | 29,638 | [7],[8] |
Investment, Identifier [Axis]: Educators Resource, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 30,000 | [5] |  |  |  |  |  |  | 30,000 | [5] | 20,000 | [8] |
Fair Value |  | 30,000 | [5] |  |  |  |  |  |  | 30,000 | [5] | 20,000 | [8] |
Investment, Identifier [Axis]: Funko Acquisition Holdings, LLC – Common Units |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [6],[7],[13] |  |  |  |  |  |  |  |  |  |  | 21 |  |
Fair Value | [6],[7],[13] |  |  |  |  |  |  |  |  |  |  | 18 |  |
Investment, Identifier [Axis]: Galaxy Technologies Holdings, Inc. – Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 11,513 | [4],[5] |  |  |  |  |  |  | 11,513 | [4],[5] | 11,513 | [7],[8] |
Fair Value |  | 3,480 | [4],[5] |  |  |  |  |  |  | 3,480 | [4],[5] | 3,368 | [7],[8] |
Investment, Identifier [Axis]: Galaxy Technologies Holdings, Inc. – Term Debt 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 6,900 | [5] |  |  |  |  |  |  | 6,900 | [5] | 6,900 | [8] |
Fair Value |  | 6,900 | [5] |  |  |  |  |  |  | 6,900 | [5] | 6,900 | [8] |
Investment, Identifier [Axis]: Galaxy Technologies Holdings, Inc. – Term Debt 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 18,796 | [5] |  |  |  |  |  |  | 18,796 | [5] | 18,796 | [8] |
Fair Value |  | 18,796 | [5] |  |  |  |  |  |  | 18,796 | [5] | 18,796 | [8] |
Investment, Identifier [Axis]: Ginsey Home Solutions, Inc. – Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 8 | [4],[5] |  |  |  |  |  |  | 8 | [4],[5] | 8 | [7],[8] |
Fair Value |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 0 | [7],[8] |
Investment, Identifier [Axis]: Ginsey Home Solutions, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 9,583 | [4],[5] |  |  |  |  |  |  | 9,583 | [4],[5] | 9,583 | [7],[8] |
Fair Value |  | 9,070 | [4],[5] |  |  |  |  |  |  | 9,070 | [4],[5] | 891 | [7],[8] |
Investment, Identifier [Axis]: Ginsey Home Solutions, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 12,200 | [5] |  |  |  |  |  |  | 12,200 | [5] | 12,200 | [8] |
Fair Value |  | 12,200 | [5] |  |  |  |  |  |  | 12,200 | [5] | 12,200 | [8] |
Investment, Identifier [Axis]: Home Concepts Acquisition, Inc. – Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 2,000 | [5] |  |  |  |  |  |  | 2,000 | [5] | 1,000 | [8] |
Fair Value |  | 2,000 | [5] |  |  |  |  |  |  | 2,000 | [5] | 1,000 | [8] |
Investment, Identifier [Axis]: Home Concepts Acquisition, Inc. – Line of Credit Two |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5] | 400 |  |  |  |  |  |  |  | 400 |  |  |  |
Fair Value | [5] | 400 |  |  |  |  |  |  |  | 400 |  |  |  |
Investment, Identifier [Axis]: Home Concepts Acquisition, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 3,275 | [4],[5] |  |  |  |  |  |  | 3,275 | [4],[5] | 3,275 | [7],[8] |
Fair Value |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 1,238 | [7],[8] |
Investment, Identifier [Axis]: Home Concepts Acquisition, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 12,000 | [5] |  |  |  |  |  |  | 12,000 | [5] | 12,000 | [8] |
Fair Value |  | 9,281 | [5] |  |  |  |  |  |  | 9,281 | [5] | 12,000 | [8] |
Investment, Identifier [Axis]: Horizon Facilities Services, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 0 | [7],[8] |
Fair Value |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 0 | [7],[8] |
Investment, Identifier [Axis]: Horizon Facilities Services, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 57,700 | [5] |  |  |  |  |  |  | 57,700 | [5] | 57,700 | [8] |
Fair Value |  | 29,634 | [5] |  |  |  |  |  |  | 29,634 | [5] | 57,700 | [8] |
Investment, Identifier [Axis]: ImageWorks Display and Marketing Group, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 6,749 | [4],[5] |  |  |  |  |  |  | 6,749 | [4],[5] | 6,749 | [7],[8] |
Fair Value |  | 12,921 | [4],[5] |  |  |  |  |  |  | 12,921 | [4],[5] | 2,607 | [7],[8] |
Investment, Identifier [Axis]: ImageWorks Display and Marketing Group, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8] |  |  |  |  |  |  |  |  |  |  | 22,000 |  |
Fair Value | [8] |  |  |  |  |  |  |  |  |  |  | 22,000 |  |
Investment, Identifier [Axis]: ImageWorks Display and Marketing Group, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5] | 22,000 |  |  |  |  |  |  |  | 22,000 |  |  |  |
Fair Value | [5] | 22,000 |  |  |  |  |  |  |  | 22,000 |  |  |  |
Investment, Identifier [Axis]: J.R. Hobbs Co. - Atlanta, LLC - Term Debt 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 16,500 | [5],[9] |  |  |  |  |  |  | 16,500 | [5],[9] | 16,500 | [8],[12] |
Fair Value |  | 10,019 | [5],[9] |  |  |  |  |  |  | 10,019 | [5],[9] | 8,852 | [8],[12] |
Investment, Identifier [Axis]: J.R. Hobbs Co. - Atlanta, LLC - Term Debt 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5],[9] | 26,000 |  |  |  |  |  |  |  | 26,000 |  |  |  |
Fair Value | [5],[9] | 15,788 |  |  |  |  |  |  |  | 15,788 |  |  |  |
Investment, Identifier [Axis]: J.R. Hobbs Co. - Atlanta, LLC - Term Debt 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5],[9] | 2,438 |  |  |  |  |  |  |  | 2,438 |  |  |  |
Fair Value | [5],[9] | 1,480 |  |  |  |  |  |  |  | 1,480 |  |  |  |
Investment, Identifier [Axis]: J.R. Hobbs Co. - Atlanta, LLC – Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 5,000 | [5],[9] |  |  |  |  |  |  | 5,000 | [5],[9] | 5,000 | [8],[12] |
Fair Value |  | 3,036 | [5],[9] |  |  |  |  |  |  | 3,036 | [5],[9] | 2,682 | [8],[12] |
Investment, Identifier [Axis]: J.R. Hobbs Co. - Atlanta, LLC – Term Debt 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8],[12] |  |  |  |  |  |  |  |  |  |  | 26,000 |  |
Fair Value | [8],[12] |  |  |  |  |  |  |  |  |  |  | 13,949 |  |
Investment, Identifier [Axis]: J.R. Hobbs Co. - Atlanta, LLC – Term Debt 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8],[12] |  |  |  |  |  |  |  |  |  |  | 2,438 |  |
Fair Value | [8],[12] |  |  |  |  |  |  |  |  |  |  | 1,308 |  |
Investment, Identifier [Axis]: J.R. Hobbs Co. – Atlanta, LLC – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 10,920 | [4],[5] |  |  |  |  |  |  | 10,920 | [4],[5] | 10,920 | [7],[8] |
Fair Value |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 0 | [7],[8] |
Investment, Identifier [Axis]: Mason West, LLC – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 11,206 | [4],[5] |  |  |  |  |  |  | 11,206 | [4],[5] | 11,206 | [7],[8] |
Fair Value |  | 13,262 | [4],[5] |  |  |  |  |  |  | 13,262 | [4],[5] | 19,759 | [7],[8] |
Investment, Identifier [Axis]: Mason West, LLC – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 25,250 | [5] |  |  |  |  |  |  | 25,250 | [5] | 25,250 | [8] |
Fair Value |  | 25,250 | [5] |  |  |  |  |  |  | 25,250 | [5] | 25,250 | [8] |
Investment, Identifier [Axis]: Nielsen-Kellerman Acquisition Corp. Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[5] | 1,070 |  |  |  |  |  |  |  | 1,070 |  |  |  |
Fair Value | [3],[5] | 1,070 |  |  |  |  |  |  |  | 1,070 |  |  |  |
Investment, Identifier [Axis]: Nielsen-Kellerman Acquisition Corp. TL - Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[5] | 48,082 |  |  |  |  |  |  |  | 48,082 |  |  |  |
Fair Value | [3],[5] | 48,082 |  |  |  |  |  |  |  | 48,082 |  |  |  |
Investment, Identifier [Axis]: Nielsen-Kellerman Acquisition Corp. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[4],[5] | 22,169 |  |  |  |  |  |  |  | 22,169 |  |  |  |
Fair Value | [3],[4],[5] | 22,421 |  |  |  |  |  |  |  | 22,421 |  |  |  |
Investment, Identifier [Axis]: Nocturne Luxury Villas, Inc. – Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8] |  |  |  |  |  |  |  |  |  |  | 4,000 |  |
Fair Value | [8] |  |  |  |  |  |  |  |  |  |  | 4,000 |  |
Investment, Identifier [Axis]: Nocturne Luxury Villas, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [7],[8] |  |  |  |  |  |  |  |  |  |  | 6,600 |  |
Fair Value | [7],[8] |  |  |  |  |  |  |  |  |  |  | 12,266 |  |
Investment, Identifier [Axis]: Nocturne Luxury Villas, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8],[14] |  |  |  |  |  |  |  |  |  |  | 61,100 |  |
Fair Value | [8],[14] |  |  |  |  |  |  |  |  |  |  | 61,100 |  |
Investment, Identifier [Axis]: Nth Degree Investment Group, LLC – Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 5,000 | [4],[15] |  |  |  |  |  |  | 5,000 | [4],[15] | 6,219 | [7],[8] |
Fair Value |  | 4,975 | [4],[15] |  |  |  |  |  |  | 4,975 | [4],[15] | 51,442 | [7],[8] |
Investment, Identifier [Axis]: Nth Degree Investment Group, LLC – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [16] |  |  |  |  |  |  |  |  |  |  | 25,000 |  |
Fair Value | [16] |  |  |  |  |  |  |  |  |  |  | 25,000 |  |
Investment, Identifier [Axis]: Old World Christmas, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 0 | [7],[8] |
Fair Value |  | 23,539 | [4],[5] |  |  |  |  |  |  | 23,539 | [4],[5] | 30,638 | [7],[8] |
Investment, Identifier [Axis]: Old World Christmas, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 38,000 | [5] |  |  |  |  |  |  | 38,000 | [5] | 43,000 | [8] |
Fair Value |  | 38,000 | [5] |  |  |  |  |  |  | 38,000 | [5] | 43,000 | [8] |
Investment, Identifier [Axis]: PSI Molded Plastics, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 36,130 | [4],[5] |  |  |  |  |  |  | 36,130 | [4],[5] | 19,730 | [7],[8] |
Fair Value |  | 996 | [4],[5] |  |  |  |  |  |  | 996 | [4],[5] | 0 | [7],[8] |
Investment, Identifier [Axis]: PSI Molded Plastics, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 10,616 | [5] |  |  |  |  |  |  | 10,616 | [5] | 26,618 | [8] |
Fair Value |  | 10,616 | [5] |  |  |  |  |  |  | 10,616 | [5] | 20,363 | [8] |
Investment, Identifier [Axis]: Phoenix Door Systems, Inc – Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8] |  |  |  |  |  |  |  |  |  |  | 2,750 |  |
Fair Value | [8] |  |  |  |  |  |  |  |  |  |  | 2,750 |  |
Investment, Identifier [Axis]: Phoenix Door Systems, Inc. – Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 1,830 | [4],[5] |  |  |  |  |  |  | 1,830 | [4],[5] | 1,830 | [7],[8] |
Fair Value |  | 0 | [4],[5] |  |  |  |  |  |  | 0 | [4],[5] | 0 | [7],[8] |
Investment, Identifier [Axis]: Phoenix Door Systems, Inc. – Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5] | 2,950 |  |  |  |  |  |  |  | 2,950 |  |  |  |
Fair Value | [5] | 2,950 |  |  |  |  |  |  |  | 2,950 |  |  |  |
Investment, Identifier [Axis]: Phoenix Door Systems, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 3,200 | [5] |  |  |  |  |  |  | 3,200 | [5] | 3,200 | [8] |
Fair Value |  | 3,200 | [5] |  |  |  |  |  |  | 3,200 | [5] | 2,817 | [8] |
Investment, Identifier [Axis]: Pyrotek Special Effects, Inc. - Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5],[17] | 2,500 |  |  |  |  |  |  |  | 2,500 |  |  |  |
Fair Value | [5],[17] | 2,500 |  |  |  |  |  |  |  | 2,500 |  |  |  |
Investment, Identifier [Axis]: Pyrotek Special Effects, Inc. - Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5],[17] | 20,120 |  |  |  |  |  |  |  | 20,120 |  |  |  |
Fair Value | [5],[17] | 20,120 |  |  |  |  |  |  |  | 20,120 |  |  |  |
Investment, Identifier [Axis]: Pyrotek Special Effects, Inc.. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [4],[5],[17] | 7,060 |  |  |  |  |  |  |  | 7,060 |  |  |  |
Fair Value | [4],[5],[17] | 7,260 |  |  |  |  |  |  |  | 7,260 |  |  |  |
Investment, Identifier [Axis]: Ricardo Defense, Inc. - Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[4],[5] | 17,388 |  |  |  |  |  |  |  | 17,388 |  |  |  |
Fair Value | [3],[4],[5] | 17,388 |  |  |  |  |  |  |  | 17,388 |  |  |  |
Investment, Identifier [Axis]: Ricardo Defense, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [3],[5] | 61,305 |  |  |  |  |  |  |  | 61,305 |  |  |  |
Fair Value | [3],[5] | 61,305 |  |  |  |  |  |  |  | 61,305 |  |  |  |
Investment, Identifier [Axis]: SFEG Holdings, Inc. – Common Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 30,746 | [4],[5] |  |  |  |  |  |  | 30,746 | [4],[5] | 30,746 | [7],[8] |
Fair Value |  | 50,788 | [4],[5] |  |  |  |  |  |  | 50,788 | [4],[5] | 38,137 | [7],[8] |
Investment, Identifier [Axis]: SFEG Holdings, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5] | 54,644 |  |  |  |  |  |  |  | 54,644 |  |  |  |
Fair Value | [5] | 54,644 |  |  |  |  |  |  |  | 54,644 |  |  |  |
Investment, Identifier [Axis]: SFEG Holdings, Inc. – Term Debt 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8] |  |  |  |  |  |  |  |  |  |  | 54,644 |  |
Fair Value | [8] |  |  |  |  |  |  |  |  |  |  | 54,644 |  |
Investment, Identifier [Axis]: Schylling, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 4,000 | [4],[5] |  |  |  |  |  |  | 4,000 | [4],[5] | 4,000 | [7],[8] |
Fair Value |  | 20,599 | [4],[5] |  |  |  |  |  |  | 20,599 | [4],[5] | 11,369 | [7],[8] |
Investment, Identifier [Axis]: Schylling, Inc. – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 27,981 | [5] |  |  |  |  |  |  | 27,981 | [5] | 27,981 | [8] |
Fair Value |  | 27,981 | [5] |  |  |  |  |  |  | 27,981 | [5] | 27,981 | [8] |
Investment, Identifier [Axis]: The E3 Company, LLC – Line of Credit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8] |  |  |  |  |  |  |  |  |  |  | 1,000 |  |
Fair Value | [8] |  |  |  |  |  |  |  |  |  |  | 1,000 |  |
Investment, Identifier [Axis]: The E3 Company, LLC – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 11,233 | [4],[5] |  |  |  |  |  |  | 11,233 | [4],[5] | 11,233 | [7],[8] |
Fair Value |  | 35,839 | [4],[5] |  |  |  |  |  |  | 35,839 | [4],[5] | 16,421 | [7],[8] |
Investment, Identifier [Axis]: The E3 Company, LLC – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5] | 33,750 |  |  |  |  |  |  |  | 33,750 |  |  |  |
Fair Value | [5] | 33,750 |  |  |  |  |  |  |  | 33,750 |  |  |  |
Investment, Identifier [Axis]: The E3 Company, LLC – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8] |  |  |  |  |  |  |  |  |  |  | 33,750 |  |
Fair Value | [8] |  |  |  |  |  |  |  |  |  |  | 33,750 |  |
Investment, Identifier [Axis]: The Maids International, LLC – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 6,640 | [4],[5] |  |  |  |  |  |  | 6,640 | [4],[5] | 6,640 | [7],[8] |
Fair Value |  | 8,410 | [4],[5] |  |  |  |  |  |  | 8,410 | [4],[5] | 5,426 | [7],[8] |
Investment, Identifier [Axis]: The Maids International, LLC – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [5] | 28,560 |  |  |  |  |  |  |  | 28,560 |  |  |  |
Fair Value | [5] | 28,560 |  |  |  |  |  |  |  | 28,560 |  |  |  |
Investment, Identifier [Axis]: The Maids International, LLC – Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [8] |  |  |  |  |  |  |  |  |  |  | 28,560 |  |
Fair Value | [8] |  |  |  |  |  |  |  |  |  |  | 28,560 |  |
Investment, Identifier [Axis]: UPB Acquisition, Inc. – Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [4],[5] | 6,000 |  |  |  |  |  |  |  | 6,000 |  |  |  |
Fair Value | [4],[5] | 26,010 |  |  |  |  |  |  |  | 26,010 |  |  |  |
Investment, Identifier [Axis]: Utah Pacific Bridge & Steel, Ltd. - Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost | [7],[8] |  |  |  |  |  |  |  |  |  |  | 6,000 |  |
Fair Value | [7],[8] |  |  |  |  |  |  |  |  |  |  | 12,287 |  |
Investment, Identifier [Axis]: Utah Pacific Bridge & Steel, Ltd. - Term Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 15,000 | [5] |  |  |  |  |  |  | 15,000 | [5] | 18,250 | [8] |
Fair Value |  | 15,000 | [5] |  |  |  |  |  |  | 15,000 | [5] | 18,250 | [8] |
Secured First Lien Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 584,026 |  |  |  |  |  |  |  | 584,026 |  | 513,425 |  |
Fair Value |  | 514,334 |  |  |  |  |  |  |  | 514,334 |  | 474,856 |  |
Preferred Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost |  | 201,487 |  |  |  |  |  |  |  | 201,487 |  | 145,070 |  |
Fair Value |  | 302,163 |  |  |  |  |  |  |  | $ 302,163 |  | $ 213,480 |  |
Funko Acquisition Holdings, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal repayments of investments |  |  |  |  |  |  |  |  | $ 21 |  |  |  |  |
Realized gain on preferred equity |  |  |  |  |  |  |  |  | 2 |  |  |  |  |
Cost |  |  |  |  |  |  |  |  | $ 21 |  |  |  |  |
Nocturne Villa Rentals, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  |  |  |  | $ 18,500 |  |  |  |  |  |
Nth Degree Investment Group, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal repayments of investments |  |  |  |  |  |  | $ 25,000 |  |  |  |  |  |  |
Realized gain on preferred equity |  |  |  |  |  |  | 42,300 |  |  |  |  |  |  |
Success fee income: |  |  |  |  |  |  | $ 100 |  |  |  |  |  |  |
Pyrotek Special Effects, Inc. ("Pyrotek") |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  |  | $ 27,200 |  |  |  |  |  |  |  |
Pyrotek Special Effects, Inc. ("Pyrotek") | Secured First Lien Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  |  | 20,100 |  |  |  |  |  |  |  |
Pyrotek Special Effects, Inc. ("Pyrotek") | Preferred Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  |  | $ 7,100 |  |  |  |  |  |  |  |
Gladstone Alternative Income Fund ("GALT") |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  | $ 5,000 |  |  |  |  |  |  |  |  |
Nielsen-Kellerman, Inc. ("Nielsen-Kellerman") |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  | 71,300 |  |  |  |  |  |  |  |  |
Nielsen-Kellerman, Inc. ("Nielsen-Kellerman") | Secured First Lien Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  | 49,100 |  |  |  |  |  |  |  |  |
Nielsen-Kellerman, Inc. ("Nielsen-Kellerman") | Preferred Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  | 22,200 |  |  |  |  |  |  |  |  |
Ricardo Defense, Inc. ("Ricardo") |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  | 78,700 |  |  |  |  |  |  |  |  |
Ricardo Defense, Inc. ("Ricardo") | Secured First Lien Debt |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  | 61,300 |  |  |  |  |  |  |  |  |
Ricardo Defense, Inc. ("Ricardo") | Preferred Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  |  | $ 17,400 |  |  |  |  |  |  |  |  |
Pyrotek Special Effects, Inc |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  | $ 3,000 |  |  |  |  |  |  |  |  |  |
Educators Resource, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of investments |  |  |  | 10,000 |  |  |  |  |  |  |  |  |  |
Dividend income |  |  |  | $ 1,800 |  |  |  |  |  |  |  |  |  |
Nocturne Luxury Villas, Inc. |  |  |  |  |  |  |  |  |  |  |  |  |  |
Summary of Investment Holdings [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal repayments of investments |  | 85,600 |  |  |  |  |  |  |  |  |  |  |  |
Realized gain on preferred equity |  | 19,800 |  |  |  |  |  |  |  |  |  |  |  |
Success fee income: |  | $ 3,500 |  |  |  |  |  |  |  |  |  |  |  |
[1] | Cumulative gross unrealized appreciation for federal income tax purposes is $183.3 million; cumulative gross unrealized depreciation for federal income tax purposes is $144.9 million. Cumulative net unrealized appreciation is $38.5 million, based on a tax cost of $940.9 million.
[2] | Cumulative gross unrealized appreciation for federal income tax purposes is $180.5 million; cumulative gross unrealized depreciation for federal income tax purposes is $115.8 million. Cumulative net unrealized appreciation is $64.7 million, based on a tax cost of $855.8 million.
[3] | One or more of our affiliated funds, Gladstone Capital Corporation and Gladstone Alternative Income Fund, co-invested with us in this portfolio company pursuant to an exemptive order granted by the U.S. Securities and Exchange Commission.
[4] | Security is non-income producing.
[5] | Fair value was based on the total enterprise value of the portfolio company, which is generally allocated to the portfolio company’s securities in order of their relative priority in the capital structure. Refer to Note 3—Investments in the accompanying Notes to Consolidated Financial Statements for additional information.
[6] | One of our affiliated funds, Gladstone Capital Corporation, co-invested with us in this portfolio company pursuant to an exemptive order granted by the U.S. Securities and Exchange Commission.
[7] | Security is non-income producing.
[8] | Fair value was based on the total enterprise value of the portfolio company, which is generally allocated to the portfolio company’s securities in order of their relative priority in the capital structure. Refer to Note 3—Investments in the accompanying Notes to Consolidated Financial Statements for additional information.
[9] | Debt security is on non-accrual status.
[10] | Fair value was based on the expected exit or payoff amount, where such event has occurred or is expected to occur imminently.
[11] | Fair value was based on an internal yield analysis or on estimates of value submitted by a third-party valuation firm. Refer to Note 3—Investments in the accompanying Notes to Consolidated Financial Statements for additional information.
[12] | Debt security is on non-accrual status.
[13] | Our investment in Funko was valued using Level 2 inputs within the ASC 820 fair value hierarchy. Our common units in Funko are convertible into class A common stock in Funko, Inc. upon meeting certain requirements. Fair value was based on the closing market price of shares of Funko, Inc. as of the reporting date, less a discount for lack of marketability. Funko, Inc. is traded on the Nasdaq Global Select Market under the trading symbol “FNKO.” Refer to Note 3—Investments in the accompanying Notes to Consolidated Financial Statements for additional information.
[14] | Debt security is subject to an interest rate ceiling.
[15] | Fair value was based on net asset value, provided by the underlying fund, as a practical expedient.
[16] | Fair value was based on internal yield analysis or on estimates of value submitted by a third-party valuation firm. Refer to Note 3—Investments in the accompanying Notes to Consolidated Financial Statements for additional information.
[17] | This portfolio company is headquartered in Ontario, Canada.

X
- Definition Investment Company, Allowance For Uncollectible Receivables + References No definition available. + Details
Name: | gain_InvestmentCompanyAllowanceForUncollectibleReceivables
Namespace Prefix: | gain_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Investment Company, Gross Receivables From Portfolio Companies + References No definition available. + Details
Name: | gain_InvestmentCompanyGrossReceivablesFromPortfolioCompanies
Namespace Prefix: | gain_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number Of Industries Invested In + References No definition available. + Details
Name: | gain_NumberOfIndustriesInvestedIn
Namespace Prefix: | gain_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number Of Investment Portfolio Company + References No definition available. + Details
Name: | gain_NumberOfInvestmentPortfolioCompany
Namespace Prefix: | gain_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number Of States Where Portfolio Company Investments Are Located + References No definition available. + Details
Name: | gain_NumberOfStatesWherePortfolioCompanyInvestmentsAreLocated
Namespace Prefix: | gain_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Proceeds from Principal Repayments Of Investments, Operating Activity + References No definition available. + Details
Name: | gain_ProceedsFromPrincipalRepaymentsOfInvestmentsOperatingActivity
Namespace Prefix: | gain_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Uncollectible Receivables Allowance, Minimum Required Day For Uncollectible Adjustment + References No definition available. + Details
Name: | gain_UncollectibleReceivablesAllowanceMinimumRequiredDayForUncollectibleAdjustment
Namespace Prefix: | gain_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 42 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-42 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-21 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-20 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-20 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of operating dividend income on securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column E)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column E)(Footnote 4)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-10 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480990/946-20-50-9 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 45 -Paragraph 39 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477346/946-830-45-39 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column E)(Footnote 6)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(1)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 + Details
Name: | us-gaap_DividendIncomeOperating
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(d)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 321 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479536/321-10-50-4 + Details
Name: | us-gaap_EquitySecuritiesFvNiRealizedGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of fee income including, but not limited to, managerial assistance, servicing of investment, and origination and commitment fees. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(1)(c)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 + Details
Name: | us-gaap_FeeIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Cost of the investment. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 55 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477439/946-210-55-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-12 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(d)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 8)(a)(3)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 11)(a)(3)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 5)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 19 -Subparagraph (3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-19 + Details
Name: | us-gaap_InvestmentOwnedAtCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in security owned. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(11)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 55 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477439/946-210-55-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-2 Reference 11: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-12 Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(d)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(2)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(2)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-1 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column A)(Footnote 1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-1 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-1 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12(Column C)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-1 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3 Reference 23: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3 Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column A)(Footnote 7)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3 Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-12B(Column C)(Footnote 9)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3 Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column A)(Footnote 1)(b)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 4)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14(Column F)(Footnote 7)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6 + Details
Name: | us-gaap_InvestmentOwnedAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of cash outflow for acquisition of investment, classified as operating activity. Includes, but is not limited to, funding, origination, drawdown, and participation in investment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 946 -SubTopic 230 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477867/946-230-45-1 + Details
Name: | us-gaap_PaymentsForPurchaseOfInvestmentOperatingActivity
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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-12 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 55 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477439/946-210-55-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480990/946-20-50-9 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-1 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (g)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478795/946-210-50-6 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478297/946-220-50-3 + Details
Name: | us-gaap_SummaryOfInvestmentHoldingsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_MajorCustomersAxis=gain_FiveLargestPortfolioInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=gain_InvestmentPortfolioBenchmarkMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc. – Common Stock Warrants
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc. – Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc. – Line of Credit 1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc. – Line of Credit 2
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc. – Term Debt 1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=B+T Group Acquisition, Inc.– Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Brunswick Bowling Products, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Brunswick Bowling Products, Inc. – Term Debt 1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Brunswick Bowling Products, Inc. – Term Debt 2
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Dema/Mai Holdings, Inc. - Preferred Equity
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Dema/Mai Holdings, Inc. – Preferred Equity
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Dema/Mai Holdings, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Diligent Delivery Systems – Common Stock Warrants
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Diligent Delivery Systems – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Edge Adhesives Holdings, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Edge Adhesives Holdings, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Edge Adhesives Holdings, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Educators Resource, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Educators Resource, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Funko Acquisition Holdings, LLC – Common Units
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Galaxy Technologies Holdings, Inc. – Common Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Galaxy Technologies Holdings, Inc. – Term Debt 1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Galaxy Technologies Holdings, Inc. – Term Debt 2
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Ginsey Home Solutions, Inc. – Common Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Ginsey Home Solutions, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Ginsey Home Solutions, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Home Concepts Acquisition, Inc. – Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Home Concepts Acquisition, Inc. – Line of Credit Two
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Home Concepts Acquisition, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Home Concepts Acquisition, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Horizon Facilities Services, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Horizon Facilities Services, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=ImageWorks Display and Marketing Group, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=ImageWorks Display and Marketing Group, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=ImageWorks Display and Marketing Group, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=J.R. Hobbs Co. - Atlanta, LLC - Term Debt 1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=J.R. Hobbs Co. - Atlanta, LLC - Term Debt 2
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=J.R. Hobbs Co. - Atlanta, LLC - Term Debt 3
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=J.R. Hobbs Co. - Atlanta, LLC – Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=J.R. Hobbs Co. - Atlanta, LLC – Term Debt 2
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=J.R. Hobbs Co. - Atlanta, LLC – Term Debt 3
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=J.R. Hobbs Co. – Atlanta, LLC – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Mason West, LLC – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Mason West, LLC – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nielsen-Kellerman Acquisition Corp. Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nielsen-Kellerman Acquisition Corp. TL - Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nielsen-Kellerman Acquisition Corp. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nocturne Luxury Villas, Inc. – Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nocturne Luxury Villas, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nocturne Luxury Villas, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nth Degree Investment Group, LLC – Common Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Nth Degree Investment Group, LLC – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Old World Christmas, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Old World Christmas, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=PSI Molded Plastics, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=PSI Molded Plastics, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Phoenix Door Systems, Inc – Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Phoenix Door Systems, Inc. – Common Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Phoenix Door Systems, Inc. – Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Phoenix Door Systems, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Pyrotek Special Effects, Inc. - Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Pyrotek Special Effects, Inc. - Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Pyrotek Special Effects, Inc.. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Ricardo Defense, Inc. - Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Ricardo Defense, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=SFEG Holdings, Inc. – Common Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=SFEG Holdings, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=SFEG Holdings, Inc. – Term Debt 1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Schylling, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Schylling, Inc. – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=The E3 Company, LLC – Line of Credit
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=The E3 Company, LLC – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=The E3 Company, LLC – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=The E3 Company, LLC – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=The Maids International, LLC – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=The Maids International, LLC – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=The Maids International, LLC – Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=UPB Acquisition, Inc. – Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Utah Pacific Bridge & Steel, Ltd. - Preferred Stock
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentIdentifierAxis=Utah Pacific Bridge & Steel, Ltd. - Term Debt
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=gain_DebtSecuritiesSecuredFirstLienDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=gain_PreferredEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_FunkoAcquisitionHoldingsLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_NocturneVillaRentalsIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_NthDegreeInvestmentGroupLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_PyrotekSpecialEffectsInc.PyrotekMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_GladstoneAlternativeIncomeFundGALTMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_NielsenKellermanInc.NielsenKellermanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_RicardoDefenseInc.RicardoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_PyrotekSpecialEffectsIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_EducatorsResourceInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gain_NocturneLuxuryVillasInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |