INVENTORIES: (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Metals at lower of average cost or market:
Finished goods	$ 79,800,000		$ 101,100,000
Work-in-process	324,700,000		297,400,000
Supplies at average cost	300,100,000		284,200,000
Total current inventory	704,648,000		682,749,000
Inventory, long-term
Long-term leach stockpiles	373,627,000		262,795,000
Leaching costs capitalized as long-term inventory of leachable material	218,700,000	157,300,000
Long-term leaching inventories recognized as cost of sales	$ 82,600,000	$ 52,500,000