Gladstone Investment Corporation Quarterly report pursuant to Section 13 or 15(d)

REGISTRATION STATEMENT AND COMMON EQUITY OFFERINGS (Details) - USD ($)	3 Months Ended	9 Months Ended
	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Aug. 31, 2022	Sep. 03, 2021
Government Assistance [Line Items]
Securities, aggregate value authorized					$ 300,000,000
Securities, remaining capacity of aggregate value authorized	$ 296,500,000	$ 296,500,000
Proceeds from issuance of common stock		3,463,000	$ 0
Common Stock ATM Program
Government Assistance [Line Items]
Sale of stock, aggregate offering price authorized				$ 50,000,000
Sale of stock, remaining capacity of authorized offering price	$ 46,500,000	$ 46,500,000
Sale of stock, number of shares sold (in shares)	212,338	241,978
Sale of stock, weighted-average gross price per share (in USD per share)	$ 14.11	$ 14.31
Sale of stock, consideration received	$ 3,000,000	$ 3,500,000
Sale of stock, weighted-average net price per share after deducting commissions and offering costs (in USD per share)	$ 13.91	$ 14.11
Proceeds from issuance of common stock	$ 3,000,000	$ 3,400,000