PROVISIONALLY PRICED SALES: (Details) lb in Millions, $ in Millions	Sep. 30, 2016 USD ($) lb $ / item
Copper
PROVISIONALLY PRICED SALES:
Provisional price sales adjustment amounts included in accounts receivable and net sales | $	$ 3.5
Copper | October 2016 to December 2016
PROVISIONALLY PRICED SALES:
Sales volume (in million lbs.) | lb	206.3
Provisional price | $ / item	2.20
Molybdenum
PROVISIONALLY PRICED SALES:
Provisional price sales adjustment amounts included in accounts receivable and net sales | $	$ (1.1)
Molybdenum | October 2016 to January 2017
PROVISIONALLY PRICED SALES:
Sales volume (in million lbs.) | lb	15.8
Provisional price | $ / item	7.00