COMMITMENTS AND CONTINGENCIES: - Labor matters (Details)	1 Months Ended						3 Months Ended			6 Months Ended
	Nov. 30, 2019 PEN (S/) agreement	Nov. 30, 2019 USD ($) agreement	Mar. 31, 2019 PEN (S/) item	Mar. 31, 2019 USD ($) item	Aug. 31, 2018 USD ($) item	Jun. 30, 2018	Dec. 31, 2018 PEN (S/)	Sep. 30, 2018 PEN (S/)	Sep. 30, 2018 USD ($)	Jun. 30, 2020 USD ($) employee item	Aug. 22, 2018 USD ($)
Year Three Collective Bargaining Agreement
Labor matters
Labor expense | $		$ 13,600
Labor Matters
Labor matters
Annual salary increase (as a percent)	5.00%	5.00%
Number of agreements signed | agreement	2	2
Labor Matters | Year One Collective Bargaining Agreement
Labor matters
Term of agreement	1 year	1 year
Labor expense	S/ 15,000	$ 4,500
Labor Matters | Year Three Collective Bargaining Agreement
Labor matters
Labor expense | S/	S/ 45,000
Peru | Labor Matters
Labor matters
Percentage of labor unionized										65.10%
Total number of workers | employee										4,848
Number of labor unions										6
Number of labor unions represent majority of workers										1
Number of labor unions other than majority workers unions										5
Term of agreement					3 years	3 years
Annual salary increase (as a percent)			5.00%	5.00%			5.00%	5.00%	5.00%
Labor expense			S/ 45,000	$ 13,600	$ 13,600		S/ 45,000	S/ 45,000	$ 13,600
Number of additional unions			1	1	3
Mexico | San Martin
Labor matters
Budgeted cost for rehabilitation of mine | $											$ 97,700,000
Total expense incurred on rehabilitation of mine till date | $										$ 81,100,000