Deferred gain on sale of royalty (Details) - USD ($) $ in Millions	Sep. 29, 2020	May 29, 2020
Other Liabilities Disclosure [Abstract]
Proceeds from royalty obligation	$ 30.0	$ 30.0
Smelter royalty obligation, percentage	1.50%	1.50%

The cash inflow associated with the assumption of a royalty obligation.

No definition available.

Name:	hymc_ProceedsFromRoyaltyObligation
Namespace Prefix:	hymc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration