INVENTORIES: (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Metals at lower of average cost or market:
Finished goods	$ 91,900,000		$ 101,100,000
Work-in-process	287,200,000		297,400,000
Supplies at average cost	303,900,000		284,200,000
Total current inventory	682,983,000		682,749,000
Inventory, long-term
Long-term Leach stockpiles	326,188,000		262,795,000
Leaching costs capitalized as long-term inventory of leachable material	142,500,000	101,200,000
Leachable material inventories recognized as cost of sales	$ 54,600,000	$ 35,300,000