Basis of Preparation of Financial Statements and Nature of Operations (Details) $ / shares in Units, $ in Thousands, shares in Millions		3 Months Ended		6 Months Ended
	Aug. 02, 2017 USD ($) $ / shares shares	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) property	Jun. 30, 2017 USD ($)
Shutdown and care and maintenance costs		$ 492	$ 369	$ 981	$ 719
Number of exploration properties | property				10
Velardena properties
Interest acquired (as a percent)		100.00%		100.00%
Shutdown and care and maintenance costs				$ 1,000	$ 700
Quarterly holding costs expected with suspended operations				400
Oxide Plant
Expected lease proceeds	$ 1,000			200
Renewal term	2 years
Proceeds from lease	$ 1,000
Gross proceeds from common stock sale	$ 1,000
Common stock issued (in shares) | shares	1.8
Sale price (in dollars per shares) | $ / shares	$ 0.55
Volume weighted average stock price period	30 days
Oxide Plant | Hecla
Expected lease proceeds				$ 4,500