Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Number of reportable segments | segment									2
Total sales, net	$ 39,348	$ 40,066	$ 29,374	$ 26,578	$ 28,131	$ 24,258	$ 30,768	$ 32,151	$ 135,366	$ 115,308	$ 110,156
Exploration expense									14,233	17,139	13,637
Net income (loss)	174	$ 2,978	$ 1,798	$ 882	858	$ (781)	$ 3,754	$ 5,457	5,832	9,288	4,150
Capital expenditures									41,482	44,201	31,856
Accrued capital expenditures									(550)	3,302	1,041
Non - cash additions									2,558	823	5,383
Capital expenditures on a cash basis									39,474	40,076	25,432
Assets	193,012				150,331				193,012	150,331
Mexico
Total sales, net									120,301	115,308	110,156
Net income (loss)									17,416	20,631	20,379
Capital expenditures									17,986	24,039	21,760
Assets	98,718				91,590				98,718	91,590
Nevada
Total sales, net									15,065
Net income (loss)									300	(2,585)	(2,423)
Capital expenditures									23,477	20,133	10,087
Assets	84,669				46,677				84,669	46,677
Corporate and Other
Net income (loss)									(11,884)	(8,758)	(13,806)
Capital expenditures									19	29	9
Assets	$ 9,625				$ 12,064				9,625	12,064
Exploration expenses
Exploration expense									3,652	4,703	4,349
Exploration expenses | Mexico
Exploration expense									2,614	2,217	1,288
Exploration expenses | Nevada
Exploration expense									932	2,314	2,916
Exploration expenses | Corporate and Other
Exploration expense									$ 106	$ 172	$ 145