SEGMENT AND RELATED INFORMATION: (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
SALES VALUE PER SEGMENT:
Net sales outside of segments	$ 1,651,100	$ 1,552,400	$ 1,659,900	$ 1,805,900	$ 1,669,300	$ 1,745,900	$ 1,801,500	$ 1,602,000	$ 6,669,266	$ 6,818,721	$ 5,149,500
Copper
SALES VALUE PER SEGMENT:
Net sales outside of segments									5,136,900	5,229,600	3,745,800
Molybdenum
SALES VALUE PER SEGMENT:
Net sales outside of segments									450,500	544,100	683,400
Silver
SALES VALUE PER SEGMENT:
Net sales outside of segments									495,300	492,400	307,700
Zinc
SALES VALUE PER SEGMENT:
Net sales outside of segments									195,900	209,800	212,500
Other:
SALES VALUE PER SEGMENT:
Net sales outside of segments									390,700	342,800	200,100
Mexican Open-pit
SALES VALUE PER SEGMENT:
Net sales outside of segments									3,338,500	3,212,100	1,648,500
Mexican Open-pit | Copper
SALES VALUE PER SEGMENT:
Net sales outside of segments									2,604,900	2,509,600	1,088,700
Mexican Open-pit | Molybdenum
SALES VALUE PER SEGMENT:
Net sales outside of segments									271,300	310,800	361,300
Mexican Open-pit | Silver
SALES VALUE PER SEGMENT:
Net sales outside of segments									280,500	248,100	142,500
Mexican Open-pit | Other:
SALES VALUE PER SEGMENT:
Net sales outside of segments									181,800	143,600	56,000
Mexican IMMSA Unit
SALES VALUE PER SEGMENT:
Net sales outside of segments									512,600	546,200	512,700
Mexican IMMSA Unit | Copper
SALES VALUE PER SEGMENT:
Net sales outside of segments									62,300	57,200	68,900
Mexican IMMSA Unit | Silver
SALES VALUE PER SEGMENT:
Net sales outside of segments									161,500	184,200	140,400
Mexican IMMSA Unit | Zinc
SALES VALUE PER SEGMENT:
Net sales outside of segments									194,900	209,800	211,700
Mexican IMMSA Unit | Other:
SALES VALUE PER SEGMENT:
Net sales outside of segments									93,900	95,000	91,700
Peruvian Operations
SALES VALUE PER SEGMENT:
Net sales outside of segments									2,952,300	3,186,500	3,125,900
Peruvian Operations | Copper
SALES VALUE PER SEGMENT:
Net sales outside of segments									2,532,000	2,720,000	2,649,700
Peruvian Operations | Molybdenum
SALES VALUE PER SEGMENT:
Net sales outside of segments									179,200	233,300	322,100
Peruvian Operations | Silver
SALES VALUE PER SEGMENT:
Net sales outside of segments									113,600	121,200	86,600
Peruvian Operations | Other:
SALES VALUE PER SEGMENT:
Net sales outside of segments									127,500	112,000	67,500
Corporate and other eliminations
SALES VALUE PER SEGMENT:
Net sales outside of segments									(134,100)	(126,100)	(137,600)
Corporate and other eliminations | Copper
SALES VALUE PER SEGMENT:
Net sales outside of segments									(62,300)	(57,200)	(61,500)
Corporate and other eliminations | Silver
SALES VALUE PER SEGMENT:
Net sales outside of segments									(60,300)	(61,100)	(61,800)
Corporate and other eliminations | Zinc
SALES VALUE PER SEGMENT:
Net sales outside of segments									1,000		800
Corporate and other eliminations | Other:
SALES VALUE PER SEGMENT:
Net sales outside of segments									$ (12,500)	$ (7,800)	$ (15,100)