Note 3 - Investments - Current Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair market value	$ 0	$ 33,758
Corporate Bond Securities [Member]
Amortized cost		33,778
Unrealized loss		(20)
Fair market value		$ 33,758

This item represents the current cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

No definition available.

Name:	hl_DebtSecuritiesAvailableForSaleAmortizedCostBasisCurrent
Namespace Prefix:	hl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant