Liquidity (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions		3 Months Ended
	Aug. 02, 2017	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents			$ 2,237	$ 2,711	$ 3,293	$ 3,250
Decrease in cash and cash equivalents			(1,056)	(539)
Shutdown and care and maintenance costs			517	489
Exploration expenditures			855	899
General and administrative expenses			1,074	1,061
Proceeds from issuance of common stock, net of issuance costs			337
Net cash used in operating activities			(1,407)	(1,760)
Other exploration and property holding costs			2,800
Contract liability related to payments			293		$ 293
Subsequent Event
Proceeds from issuance of common stock, net of issuance costs		$ 100
Forecast
Net operating margin		$ 4,800
Velardena properties
Shutdown and care and maintenance costs			500	$ 500
Oxide Plant
Net operating margin			1,300
Registered direct purchase agreement, net (in shares)	1.8
Sale price (in dollars per shares)	$ 0.55
Gross proceeds from common stock sale	$ 1,000
El Quevar Project
Maintenance and property holding costs			1,000
Other exploration and property holding costs			300
LPC Program
General and administrative expenses			3,000
Other exploration and property holding costs			400
Electrum | Velardena properties
Shutdown and care and maintenance costs			$ 1,500