Note 5 - Environmental and Reclamation Activities - Liabilities Accrued for Reclamation and Closure Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclamation and closure costs	$ 108,389	$ 86,045	$ 85,580	$ 95,538
Reclamation and closure costs, current	(3,410)	(6,679)
Reclamation and closure costs, long-term	104,979	79,366
Operating Properties [Member] | Greens Creek [Member]
Reclamation and closure costs	41,839	41,677
Operating Properties [Member] | Lucky Friday [Member]
Reclamation and closure costs	10,698	9,911
Operating Properties [Member] | Casa Berardi [Member]
Reclamation and closure costs	5,843	6,729
Operating Properties [Member] | San Sebastian [Member]
Reclamation and closure costs	7,765	5,067
Operating Properties [Member] | Nevada Operations [Member]
Reclamation and closure costs	23,272
Non-Operating Properties [Member] | Troy Mine [Member]
Reclamation and closure costs	8,971	12,724
Non-Operating Properties [Member] | Johnny M Mine Area near San Mateo, New Mexico [Member]
Reclamation and closure costs	5,813	5,813
Non-Operating Properties [Member] | Republic [Member]
Reclamation and closure costs	1,500	1,500
Non-Operating Properties [Member] | All Other Sites [Member]
Reclamation and closure costs	$ 2,688	$ 2,624