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

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Thousands																				1 Months Ended					3 Months Ended	6 Months Ended
	Dec. 30, 2022	Dec. 15, 2022	Nov. 30, 2022	Oct. 31, 2022	Sep. 30, 2022	Aug. 31, 2022	Jul. 29, 2022	Jun. 30, 2022	Jun. 15, 2022	May 31, 2022	Apr. 29, 2022	Sep. 30, 2021	Sep. 15, 2021	Aug. 31, 2021	Jul. 30, 2021	Jun. 30, 2021	Jun. 17, 2021	May 28, 2021	Apr. 30, 2021	Oct. 31, 2022	Aug. 31, 2022	Jul. 31, 2022	Jun. 30, 2022	May 31, 2022	Dec. 31, 2022	Sep. 30, 2022	Sep. 30, 2021
Subsequent Event [Line Items]
Purchase of investments																										$ 102,046	$ 47,550
Common stock dividends paid (in USD per share)					$ 0.075	$ 0.075	$ 0.075	$ 0.075	$ 0.120	$ 0.075	$ 0.075	$ 0.070	$ 0.030	$ 0.070	$ 0.070	$ 0.070	$ 0.060	$ 0.070	$ 0.070							$ 0.570	$ 0.510
Investment, Identifier [Axis]: Dema/Mai Holdings, Inc.
Subsequent Event [Line Items]
Purchase of investments																						$ 39,100	$ 21,000
Investment, Identifier [Axis]: Ginsey Home Solutions, Inc.
Subsequent Event [Line Items]
Purchase of investments																					$ 4,000
Investment, Identifier [Axis]: Horizon Facilities Services, Inc. \| Secured First Lien Debt
Subsequent Event [Line Items]
Purchase of investments																						$ 30,000
Investment, Identifier [Axis]: Nocturne Villa Rentals, Inc. \| Secured First Lien Debt
Subsequent Event [Line Items]
Purchase of investments																								$ 6,400
Subsequent Event
Subsequent Event [Line Items]
Common stock dividends paid (in USD per share)				$ 0.080
Subsequent Event \| Forecast
Subsequent Event [Line Items]
Common stock dividends paid (in USD per share)	$ 0.080	$ 0.120	$ 0.080																						$ 0.360
Subsequent Event \| Investment, Identifier [Axis]: Nocturne Villa Rentals, Inc. \| Secured First Lien Debt
Subsequent Event [Line Items]
Purchase of investments																				$ 8,400