Note 10 - Commitments, Contingencies and Obligations (Details Textual) - USD ($)			1 Months Ended			3 Months Ended			9 Months Ended
	Jul. 12, 2022	Jun. 30, 2022	Jul. 31, 2018	Aug. 31, 2012	Jun. 30, 2011	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Environmental Remediation Expense						$ 1,781,000	$ 7,564,000		$ 4,154,000	$ 12,297,000
Finance Lease, Liability, to be Paid, Total						22,298,000			22,298,000
Lessee, Operating Lease, Liability, to be Paid, Total						13,648,000			13,648,000
Lease Commitments [Member]
Finance Lease, Liability, to be Paid, Total						22,300,000			22,300,000
Lessee, Operating Lease, Liability, to be Paid, Total						13,600,000			13,600,000
Performance Obligation Commitments [Member]
Surety Bonds						193,800,000			193,800,000
Letters of Credit Outstanding, Amount						7,800,000			7,800,000
Greens Creek [Member]
EPA Maximum for Statutory Penalties, Per Day/Violation		$ 81,540,000
EPA Maximum for Administrative Penalties, Per Day/Violation		$ 47,423,000
Greens Creek [Member] | Purchase Orders and Commitment [Member]
Contractual Obligation, Total						9,000,000			9,000,000
Lucky Friday [Member]
EPA Maximum for Statutory Penalties, Per Day/Violation	$ 59,973,000
EPA Maximum for Administrative Penalties, Per Day/Violation	23,989,000
EPA Maximum for Administrative Penalties, Total	$ 299,989,000
Lucky Friday [Member] | Purchase Orders and Commitment [Member]
Contractual Obligation, Total						20,400,000			20,400,000
Casa Berardi [Member] | Purchase Orders and Commitment [Member]
Contractual Obligation, Total						1,200,000			1,200,000
Nevada Operations [Member] | Purchase Orders and Commitment [Member]
Contractual Obligation, Total						2,600,000			2,600,000
Keno Hill [Member] | Purchase Orders and Commitment [Member]
Contractual Obligation, Total						$ 300,000			$ 300,000
Johnny M Mine Area near San Mateo, New Mexico [Member]
Payment Of Response Costs				$ 1,100,000
Estimated Response Costs			$ 9,600,000					$ 9,000,000
Environmental Remediation Expense								9,000,000
Johnny M Mine Area near San Mateo, New Mexico [Member] | Environmental Remediation, Past Response Costs [Member]
Accrual for Environmental Loss Contingencies, Period Increase (Decrease), Total								$ 2,900,000
Carpenter Snow Creek Superfund Site, Cascade County, Montana [Member]
Estimated Response Costs					$ 4,500,000
Estimated Future Response Cost					$ 100,000,000