Summary of Significant Accounting Policies - Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Net (loss) income from continuing operations	$ (239)	$ 29,693	$ 2,519	$ 20,190
Less: net income (loss) attributable to non-controlling interest, continuing operations	111	18	111	(1,554)
Numerator for basic EPS - Net (loss) income from continuing operations attributable to Great Elm Group, Inc.	(350)	29,675	2,408	21,744
Net income from discontinued operations		35	16	999
Less: net income attributable to non-controlling interest, discontinued operations		180		1,504
Numerator for basic EPS - Net income (loss) from discontinued operations, attributable to Great Elm Group, Inc.		(145)	16	(505)
Effect of dilutive securities:
Interest expense associated with Convertible Notes, continuing operations		480		960
Numerator for diluted EPS - Net (loss) income from continuing operations attributable to Great Elm Group, Inc., after the effect of dilutive securities	$ (350)	30,155	2,408	22,704
Numerator for diluted EPS - Net income (loss) from discontinued operations, attributable to Great Elm Group, Inc.		$ (145)	$ 16	$ (505)
Denominator:
Denominator for basic EPS - Weighted average shares of common stock outstanding	29,889	28,803	29,734	28,672
Effect of dilutive securities:
Restricted stock		1,131	1,182	1,131
Convertible Notes		10,652		10,652
Denominator for diluted EPS - Weighted average shares of common stock outstanding after the effect of dilutive securities	29,889	40,586	30,916	40,455
Basic net income (loss) per share from:
Continuing operations	$ (0.01)	$ 1.03	$ 0.08	$ 0.76
Discontinued operations		(0.01)		(0.02)
Basic net income (loss) per share	(0.01)	1.02	0.08	0.74
Diluted net income (loss) per share from:
Continuing operations	(0.01)	0.74	0.08	0.56
Discontinued operations				(0.01)
Diluted net income (loss) per share	$ (0.01)	$ 0.74	$ 0.08	$ 0.55