Note 15 - Accumulated Other Comprehensive Loss (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($)
Impact of Adoption of Accounting Standard Update	$ 0
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Impact of Adoption of Accounting Standard Update	$ (1,300)

Represents the reclassification from retained earnings to AOCI during the period related to the adoption of an accounting standards update.

No definition available.

Name:	hl_ImpactOfAdoptionOfAccountingStandardUpdate
Namespace Prefix:	hl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration