Note 4 - Environmental and Reclamation Activities - Liabilities Accrued for Reclamation and Closure Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclamation and closure costs	$ 108,374	$ 108,389	$ 86,045	$ 85,580
Reclamation and closure costs, current	(4,581)	(3,410)
Reclamation and closure costs, long-term	103,793	104,979
Operating Properties [Member] | Greens Creek [Member]
Reclamation and closure costs	44,695	41,839
Operating Properties [Member] | Lucky Friday [Member]
Reclamation and closure costs	10,473	10,698
Operating Properties [Member] | Casa Berardi [Member]
Reclamation and closure costs	4,510	5,843
Operating Properties [Member] | San Sebastian [Member]
Reclamation and closure costs	7,399	7,765
Operating Properties [Member] | Nevada Operations [Member]
Reclamation and closure costs	24,754	23,272
Non-Operating Properties [Member] | Troy Mine [Member]
Reclamation and closure costs	6,069	8,971
Non-Operating Properties [Member] | Johnny M Mine Area near San Mateo, New Mexico [Member]
Reclamation and closure costs	6,065	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	$ 2,909	$ 2,688