Note 4 - Environmental and Reclamation Activities - Liabilities Accrued for Reclamation and Closure Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating properties:
Reclamation and closure costs	$ 86,045	$ 85,580	$ 95,538	$ 57,250
Non-operating properties:
Reclamation and closure costs	86,045	85,580	$ 95,538	$ 57,250
Reclamation and closure costs, current	(6,679)	(5,653)
Reclamation and closure costs, long-term	79,366	79,927
Operating Properties [Member] | Greens Creek [Member]
Operating properties:
Reclamation and closure costs	41,677	39,014
Non-operating properties:
Reclamation and closure costs	41,677	39,014
Operating Properties [Member] | Lucky Friday [Member]
Operating properties:
Reclamation and closure costs	9,911	9,194
Non-operating properties:
Reclamation and closure costs	9,911	9,194
Operating Properties [Member] | Casa Berardi [Member]
Operating properties:
Reclamation and closure costs	6,729	5,475
Non-operating properties:
Reclamation and closure costs	6,729	5,475
Operating Properties [Member] | San Sebastian [Member]
Operating properties:
Reclamation and closure costs	5,067	5,592
Non-operating properties:
Reclamation and closure costs	5,067	5,592
Non-Operating Properties [Member] | Troy Mine [Member]
Operating properties:
Reclamation and closure costs	12,724	16,167
Non-operating properties:
Reclamation and closure costs	12,724	16,167
Non-Operating Properties [Member] | Johnny M Mine Area near San Mateo, New Mexico [Member]
Operating properties:
Reclamation and closure costs	5,813	5,830
Non-operating properties:
Reclamation and closure costs	5,813	5,830
Non-Operating Properties [Member] | Republic [Member]
Operating properties:
Reclamation and closure costs	1,500	1,500
Non-operating properties:
Reclamation and closure costs	1,500	1,500
Non-Operating Properties [Member] | All Other Sites [Member]
Operating properties:
Reclamation and closure costs	2,624	2,808
Non-operating properties:
Reclamation and closure costs	$ 2,624	$ 2,808