Summary of Significant Accounting Policies - Summary of Impact of New Accounting Standards on Financial Statements (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020
Liabilities
Convertible notes								$ 33,333
Other liabilities								915
Total Liabilities		$ 90,485		$ 90,485				106,445
Stockholders' equity
Additional paid-in-capital								3,307,613
Accumulated deficit		(3,274,750)		(3,274,750)				(3,264,403)
Total Great Elm Group, Inc Stockholder's Equity		34,981		34,981				43,236
Total Stockholder's Equity		44,718	$ 53,412	44,718	$ 53,412	$ 49,702	$ 53,794	52,785	$ 51,013	$ 49,505	$ 52,731
Non-operating expenses
Interest expense		(1,354)	(1,361)	(4,078)	(3,607)
Net loss from continuing operations
Net loss from continuing operations		$ (6,135)	$ (2,818)	$ (10,188)	$ (7,440)
Net loss per share (basic and diluted)		$ (0.22)	$ (0.10)	$ (0.38)	$ (0.25)
Previously Reported
Liabilities
Convertible notes	[1]							22,054
Other liabilities	[1]							1,070
Total Liabilities	[1]							95,321
Stockholders' equity
Additional paid-in-capital	[1]							3,319,767
Accumulated deficit	[1]							(3,265,433)
Total Great Elm Group, Inc Stockholder's Equity	[1]							54,360
Total Stockholder's Equity	[1]							63,909
Non-operating expenses
Interest expense	[1]		$ (1,534)		$ (4,105)
Net loss from continuing operations
Net loss from continuing operations	[1]		$ (2,991)		$ (7,938)
Net loss per share (basic and diluted)	[1]		$ (0.11)		$ (0.27)
Adjustment | ASU 2020-06 Adjustment
Liabilities
Convertible notes								11,279
Other liabilities								(155)
Total Liabilities								11,124
Stockholders' equity
Additional paid-in-capital								(12,154)
Accumulated deficit								1,030
Total Great Elm Group, Inc Stockholder's Equity								(11,124)
Total Stockholder's Equity								$ (11,124)
Non-operating expenses
Interest expense			$ 173		$ 498
Net loss from continuing operations
Net loss from continuing operations			$ 173		$ 498
Net loss per share (basic and diluted)			$ 0.01		$ 0.02

[1] As re-casted to reflect the operations of our real estate business as discontinued operations and therefore excluded