Asset Retirement Obligation and Reclamation Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jun. 30, 2012
Asset retirement and reclamation liabilities	$ 2,683
Summary of activity in the Velardena Operations ARO
ARO, Beginning balance	2,683
Accretion expense	55	$ 51
ARO, Ending balance	2,675
Velardena properties
Asset retirement and reclamation liabilities	2,660	2,448	$ 1,900
Summary of activity in the Velardena Operations ARO
ARO, Beginning balance	2,660	2,448
Changes in estimates, and other	(60)	1
Accretion expense	55	51
ARO, Ending balance	$ 2,655	$ 2,500