Non-Controlling Interests and Preferred Stock of Subsidiaries - Summary of Preferred Stock of Subsidiary Balances on Condensed Consolidated Balance Sheets (Details)	3 Months Ended
	Sep. 30, 2021 shares
Minority Interest [Line Items]
Balance, as of June 30, 2021	79,110,000
Issuance of Preferred Stock	0
Balance, as of September 30, 2021	79,110,000
Great Elm Healthcare, LLC (HC LLC)
Minority Interest [Line Items]
Balance, as of June 30, 2021	44,100,000
Balance, as of September 30, 2021	44,100,000
Series A-1 Preferred Stock | Great Elm Healthcare, LLC (HC LLC)
Minority Interest [Line Items]
Balance, as of June 30, 2021	10,090,000
Balance, as of September 30, 2021	10,090,000
Series A-2 Preferred Stock | Great Elm Healthcare, LLC (HC LLC)
Minority Interest [Line Items]
Balance, as of June 30, 2021	34,010,000
Balance, as of September 30, 2021	34,010,000
Forest Preferred Stock | Forest Investments, Inc. (Forest)
Minority Interest [Line Items]
Balance, as of June 30, 2021	35,010,000
Balance, as of September 30, 2021	35,010,000