Gladstone Investment Corporation Annual report [Section 13 and 15(d), not S-K Item 405]

Annual report [Section 13 and 15(d), not S-K Item 405]

BORROWINGS - Notes Payable Narrative (Details)

BORROWINGS - Notes Payable Narrative (Details) - USD ($) $ in Thousands		1 Months Ended
	Dec. 16, 2025	Feb. 28, 2026	Nov. 30, 2025	Dec. 31, 2024	May 31, 2023	Aug. 31, 2021	Mar. 31, 2021	May 01, 2026	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Debt Instrument [Line Items]
Total borrowings, at cost							$ 155,434		$ 572,888	$ 463,738	$ 404,238	$ 297,688	$ 267,584	$ 54,296	$ 58,096	$ 112,096	$ 74,796
Notes Payable
Debt Instrument [Line Items]
Total borrowings, at cost									$ 548,988	$ 463,738
5.00% Notes Due 2026 \| Notes Payable
Debt Instrument [Line Items]
Interest Rate							5.00%		5.00%	5.00%
Total borrowings, at cost							$ 127,900		$ 127,938	$ 127,938
Proceeds from issuance of long-term debt							123,800
Total underwriting discounts, commissions, and offering costs							$ 4,100
Notes payable, fair value disclosure									$ 129,000	$ 127,500
5.00% Notes Due 2026 \| Notes Payable \| Subsequent Event
Debt Instrument [Line Items]
Total borrowings, at cost								$ 127,900
4.875% Notes Due 2028 \| Notes Payable
Debt Instrument [Line Items]
Interest Rate						4.875%			4.875%	4.875%
Total borrowings, at cost						$ 134,600			$ 134,550	$ 134,550
Proceeds from issuance of long-term debt						131,300
Total underwriting discounts, commissions, and offering costs						$ 3,300
Notes payable, fair value disclosure									$ 127,800	$ 125,000
8.00% Notes Due 2028 \| Notes Payable
Debt Instrument [Line Items]
Interest Rate					8.00%					8.00%
Total borrowings, at cost					$ 74,800					$ 74,750
Proceeds from issuance of long-term debt					72,300
Percentage of principal amount redeemed	100.00%
Loss on extinguishment of debt					$ 1,300
Notes payable, fair value disclosure										$ 77,500
7.875% Notes Due 2030 \| Notes Payable
Debt Instrument [Line Items]
Interest Rate				7.875%					7.875%	7.875%
Total borrowings, at cost				$ 126,500					$ 126,500	$ 126,500
Proceeds from issuance of long-term debt				122,400
Total underwriting discounts, commissions, and offering costs				$ 4,100
Notes payable, fair value disclosure									$ 128,200	$ 128,500
6.875% Notes Due 2028 \| Notes Payable
Debt Instrument [Line Items]
Interest Rate			6.875%						6.875%
Total borrowings, at cost			$ 60,000						$ 60,000
Proceeds from issuance of long-term debt			58,800
Total underwriting discounts, commissions, and offering costs			$ 1,200
Notes payable, fair value disclosure									$ 59,700
6.875% Notes Due 2028 \| Notes Payable \| Discount Rate
Debt Instrument [Line Items]
Debt instrument, measurement input									0.07075
7.125% Notes Due 2031 \| Notes Payable
Debt Instrument [Line Items]
Interest Rate		7.125%							7.125%
Total borrowings, at cost		$ 100,000							$ 100,000
Proceeds from issuance of long-term debt		96,900
Total underwriting discounts, commissions, and offering costs		$ 3,100
Notes payable, fair value disclosure									$ 101,300