Note 8 - Employee Benefit Plans - Fair Value by Asset Category (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Hecla Mining Company Retirement Plan [Member]
Total fair value	$ 79,557	$ 68,684
Lucky Friday Pension Plan [Member]
Total fair value	20,365	18,673
Fair Value, Inputs, Level 1 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	51,300	45,223
Fair Value, Inputs, Level 1 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	12,626	12,307
Fair Value, Inputs, Level 2 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	14,802	12,379
Fair Value, Inputs, Level 2 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	4,115	3,427
Fair Value, Inputs, Level 3 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	13,455	11,082
Fair Value, Inputs, Level 3 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	3,624	2,939
Interest-bearing Deposits [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	351	1,924
Interest-bearing Deposits [Member] | Lucky Friday Pension Plan [Member]
Total fair value	100	550
Interest-bearing Deposits [Member] | Fair Value, Inputs, Level 1 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	351	1,924
Interest-bearing Deposits [Member] | Fair Value, Inputs, Level 1 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	100	550
Interest-bearing Deposits [Member] | Fair Value, Inputs, Level 2 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Interest-bearing Deposits [Member] | Fair Value, Inputs, Level 2 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Interest-bearing Deposits [Member] | Fair Value, Inputs, Level 3 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Interest-bearing Deposits [Member] | Fair Value, Inputs, Level 3 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Common Stock [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	3,768	4,973
Common Stock [Member] | Lucky Friday Pension Plan [Member]
Total fair value	1,015	1,340
Common Stock [Member] | Fair Value, Inputs, Level 1 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	3,768	4,973
Common Stock [Member] | Fair Value, Inputs, Level 1 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	1,015	1,340
Common Stock [Member] | Fair Value, Inputs, Level 2 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Common Stock [Member] | Fair Value, Inputs, Level 2 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Common Stock [Member] | Fair Value, Inputs, Level 3 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Common Stock [Member] | Fair Value, Inputs, Level 3 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Real Estate Investments [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	11,154	8,974
Real Estate Investments [Member] | Lucky Friday Pension Plan [Member]
Total fair value	3,023	2,389
Real Estate Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Real Estate Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Real Estate Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Real Estate Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Real Estate Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	11,154	8,974
Real Estate Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	3,023	2,389
Common Collective Funds [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	17,103	14,487
Common Collective Funds [Member] | Lucky Friday Pension Plan [Member]
Total fair value	4,716	3,977
Common Collective Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Common Collective Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Common Collective Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	14,802	12,379
Common Collective Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	4,115	3,427
Common Collective Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	2,301	2,108
Common Collective Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	601	550
Mutual Funds [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	47,181	38,326
Mutual Funds [Member] | Lucky Friday Pension Plan [Member]
Total fair value	11,511	10,417
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value	47,181	38,326
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Lucky Friday Pension Plan [Member]
Total fair value	11,511	10,417
Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Lucky Friday Pension Plan [Member]
Total fair value
Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Hecla Mining Company Retirement Plan [Member]
Total fair value
Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Lucky Friday Pension Plan [Member]
Total fair value