Summary of Significant Accounting Policies - Summary of Impact of New Accounting Standards on Financial Statements (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Jun. 30, 2022	Jun. 30, 2021		Jun. 30, 2020
Liabilities
Convertible notes	[1]		$ 33,333
Other liabilities	[1]		915
Total Liabilities		$ 125,833	106,445	[1]
Stockholders' equity
Additional paid-in-capital	[1]		3,307,613
Accumulated deficit		(3,279,296)	(3,264,403)	[1]
Total Great Elm Group, Inc Stockholder's Equity		33,496	43,236	[1]
Total Stockholder's Equity		40,029	52,785	[1]	$ 52,747
Non-operating expenses
Interest expense		(5,786)	(4,949)	[1]
Net loss from continuing operations
Loss from continuing operations, before income taxes		(15,016)	(6,844)	[1]
Income tax expense		(21)	(1,675)	[1]
Loss from continuing operations		(15,037)	(8,519)	[1]
Discontinued operations:
Income from discontinued operations, net of tax	[1]		649
Net loss		(15,037)	(7,870)	[1]
Less: net loss attributable to non-controlling interest, continuing operations		(144)	(648)	[1]
Less: net income attributable to non-controlling interest, discontinued operations	[1]		53
Net loss attributable to Great Elm Group		$ (14,893)	$ (7,275)	[1]
Net loss per share, basic		$ (0.56)	$ (0.28)	[1]
Net loss per share, diluted		$ (0.56)	$ (0.28)	[1]
Non-cash interest and amortization of capitalized issuance costs		$ 2,117	$ 1,851	[1]
Deferred tax expense		(85)	546	[1]
Net cash provided by (used in) operating activities - continuing operations		29,280	(20,907)	[1]
Net cash provided by operating activities - discontinued operations	[1]		1,931
Net cash provided by (used in) operating activities		29,280	(18,976)	[1]
Net cash used in investing activities - continuing operations		(40,047)	(19,839)	[1]
Net cash provided by investing activities - discontinued operations	[1]		4,357
Net cash used in investing activities		(40,047)	(15,482)	[1]
Net cash provided by financing activities - continuing operations		9,980	20,666	[1]
Net cash used in financing activities - discontinued operations	[1]		(2,326)
Net cash provided by financing activities		9,980	18,340	[1]
Net increase (decrease) in cash and cash equivalents		(787)	(16,118)	[1]
Cash and cash equivalents at beginning of year	[1]	24,382	40,500
Cash and cash equivalents at end of year		23,595	24,382	[1]
Accumulated Deficit
Stockholders' equity
Total Stockholder's Equity		(3,279,296)	(3,264,403)	[1]	(3,257,128)
Total Great Elm Group Inc. Stockholders' Equity
Stockholders' equity
Total Stockholder's Equity		33,496	43,236	[1]	$ 48,861
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]		(5,620)
Net loss from continuing operations
Loss from continuing operations, before income taxes	[1]		(7,515)
Income tax expense	[1]		(1,813)
Loss from continuing operations	[1]		(9,328)
Discontinued operations:
Income from discontinued operations, net of tax	[1]		649
Net loss	[1]		(8,679)
Less: net loss attributable to non-controlling interest, continuing operations	[1]		(648)
Less: net income attributable to non-controlling interest, discontinued operations	[1]		53
Net loss attributable to Great Elm Group	[1]		$ (8,084)
Net loss per share, basic	[1]		$ (0.31)
Net loss per share, diluted	[1]		$ (0.31)
Non-cash interest and amortization of capitalized issuance costs	[1]		$ 2,522
Deferred tax expense	[1]		684
Net cash provided by (used in) operating activities - continuing operations	[1]		(20,907)
Net cash provided by operating activities - discontinued operations	[1]		1,931
Net cash provided by (used in) operating activities	[1]		(18,976)
Net cash used in investing activities - continuing operations	[1]		(19,839)
Net cash provided by investing activities - discontinued operations	[1]		4,357
Net cash used in investing activities	[1]		(15,482)
Net cash provided by financing activities - continuing operations	[1]		20,666
Net cash used in financing activities - discontinued operations	[1]		(2,326)
Net cash provided by financing activities	[1]		18,340
Net increase (decrease) in cash and cash equivalents	[1]		(16,118)
Cash and cash equivalents at beginning of year	[1]	$ 24,382	40,500
Cash and cash equivalents at end of year	[1]		24,382
Previously Reported | Accumulated Deficit
Stockholders' equity
Total Stockholder's Equity	[1]		(3,265,433)
Previously Reported | Total Great Elm Group Inc. Stockholders' Equity
Stockholders' equity
Total Stockholder's Equity	[1]		54,360
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			671
Net loss from continuing operations
Loss from continuing operations, before income taxes			671
Income tax expense			138
Loss from continuing operations			809
Discontinued operations:
Net loss			809
Net loss attributable to Great Elm Group			$ 809
Net loss per share, basic			$ 0.03
Net loss per share, diluted			$ 0.03
Non-cash interest and amortization of capitalized issuance costs			$ (671)
Deferred tax expense			(138)
Adjustment | ASU 2020-06 Adjustment | Accumulated Deficit
Stockholders' equity
Total Stockholder's Equity			1,030
Adjustment | ASU 2020-06 Adjustment | Total Great Elm Group Inc. Stockholders' Equity
Stockholders' equity
Total Stockholder's Equity			$ (11,124)

[1] The As Reported column refects amounts originally reported in our Form 10-K filed on September 21, 2021. The As Adjusted column reflects recast amounts reported in our Form 8-K filed on May 5, 2022.