Note 5 - Environmental and Reclamation Activities - Liabilities Accrued for Reclamation and Closure Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclamation and closure costs	$ 116,048	$ 108,374	$ 108,389	$ 86,045
Reclamation and closure costs, current	(5,582)	(4,581)
Reclamation and closure costs, long-term	110,466	103,793
Operating Properties [Member] | Greens Creek [Member]
Reclamation and closure costs	42,716	44,695
Operating Properties [Member] | Lucky Friday [Member]
Reclamation and closure costs	12,818	10,473
Operating Properties [Member] | Casa Berardi [Member]
Reclamation and closure costs	11,730	4,510
Operating Properties [Member] | San Sebastian [Member]
Reclamation and closure costs	6,882	7,399
Operating Properties [Member] | Nevada Operations [Member]
Reclamation and closure costs	26,062	24,754
Non-Operating Properties [Member] | Troy Mine [Member]
Reclamation and closure costs	5,340	6,069
Non-Operating Properties [Member] | Johnny M Mine Area near San Mateo, New Mexico [Member]
Reclamation and closure costs	6,065	6,065
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	$ 2,935	$ 2,909