COMMITMENTS AND CONTINGENCIES: - Labor matters (Details)	1 Months Ended				3 Months Ended	12 Months Ended
	Aug. 31, 2018 PEN (S/) item	Aug. 31, 2018 USD ($) item	Jun. 30, 2018 PEN (S/)	Jun. 30, 2018 USD ($)	Mar. 31, 2016	Dec. 31, 2018 USD ($) item	Aug. 22, 2018 USD ($)
Peru | Labor Matters
Labor matters
Percentage of labor unionized						75.00%
Total number of workers						4,850
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	3 years	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	S/ 45,000	$ 13,600
Number of additional unions	3	3
Number of unsigned unions						2
Mexico | San Martin
Labor matters
Budgeted cost for rehabilitation of mine | $							$ 77,000,000
Total expense incurred on rehabilitation of mine till date | $						$ 17,700,000