FINANCING: (Details) (USD $)	12 Months Ended			89 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2012 item
FINANCING
Total debt	$ 4,204,900,000	$ 4,213,900,000
Less, current portion		(10,000,000)
Total long-term debt	4,204,915,000	4,203,863,000
Face amount of debt				4,200,000,000
Number of times for which senior unsecured notes were issued				6
Debt issuance cost capitalized	26,100,000	25,900,000
Amortization charged to interest expense	1,900,000	1,300,000	500,000
Percentage of principal amount at which notes may be required to be repurchased in event of change of control in the entity	101.00%
Minimum
FINANCING
Number of rating agencies that could cause a change of control triggering event	1
Number of decreased gradations that could cause a change of control triggering event	1
1.763% Mitsui credit agreement due 2013
FINANCING
Total debt		10,000,000
Face amount of debt		100,000,000
Interest rate (as a percent)	1.763%
Volume of copper on pledged receivables (in tons)	31,000
6.375% Senior unsecured notes due 2015
FINANCING
Total debt	199,700,000	199,600,000
Face amount of debt	200,000,000
Interest rate (as a percent)	6.375%
5.375% Senior unsecured notes due 2020
FINANCING
Total debt	398,600,000	398,400,000
Face amount of debt	400,000,000
Interest rate (as a percent)	5.375%
3.500% Senior unsecured notes due 2022
FINANCING
Total debt	299,100,000	299,000,000
Face amount of debt	300,000,000
Interest rate (as a percent)	3.50%
6.750% Senior unsecured notes due 2040
FINANCING
Total debt	1,092,100,000	1,092,000,000
Face amount of debt	1,100,000,000
Interest rate (as a percent)	6.75%
5.250% Senior unsecured notes due 2042
FINANCING
Total debt	1,178,800,000	1,178,500,000
Face amount of debt	1,200,000,000
Interest rate (as a percent)	5.25%
9.250% Yankee Bonds due 2028
FINANCING
Total debt	51,100,000	51,100,000
Face amount of debt	125,000,000
Interest rate (as a percent)	9.25%
9.250% Yankee Bonds due 2028 | Minera Mexico | Minimum
FINANCING
Ratio of EBITDA to interest expense	2.5
7.500% Senior unsecured notes due 2035
FINANCING
Total debt	985,500,000	985,300,000
Face amount of debt	1,000,000,000
Interest rate (as a percent)	7.50%
Debt issuance cost capitalized	$ 28,900,000