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Note 4 - Environmental and Reclamation Activities - Accrued Reclamation and Closure Cost Liability Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance	$ 85,580	$ 95,538	$ 57,250
Accruals for estimated costs	16	705	15,114
Accretion expense	4,870	3,158	1,904
Revision of estimated cash flows due to changes in reclamation plans	(578)	2,759	4,112
Addition due to development and production at our San Sebastian unit			1,189
Payment of reclamation obligations	(3,843)	(17,704)	(1,544)
Balance	$ 86,045	85,580	95,538
Revett Mining Company, Inc. [Member]
Liability addition due to acquisition of Revett			$ 17,513
Mines Management [Member]
Liability addition due to acquisition of Revett		$ 1,124