SEGMENT AND RELATED INFORMATION: (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
SEGMENT AND RELATED INFORMATION:
Number of reportable segments | segment			3
Financial information relating to segments
Net sales outside of segments	$ 1,133,602	$ 1,474,647	$ 3,791,332	$ 4,316,442
Cost of sales (exclusive of depreciation, amortization and depletion)	670,742	729,506	2,057,432	2,097,989
Selling, general and administrative	23,578	26,282	73,410	76,177
Depreciation, amortization and depletion	131,576	113,923	373,841	340,467
Exploration	13,743	20,638	36,142	57,317
Environmental remediation	7,043	37,163	23,503	37,163
Operating income	286,920	547,135	1,227,004	1,707,329
Interest, net	(61,900)	(30,800)	(136,100)	(100,000)
Other (expense) income	(4,297)	(21,066)	(9,666)	(31,051)
Income taxes	(125,336)	(175,405)	(411,571)	(605,336)
Equity earnings of affiliate	4,039	5,926	9,454	17,825
Non-controlling interest	(962)	(1,463)	(3,518)	(3,800)
Net income attributable to SCC	98,437	324,317	675,581	984,959
Capital investment	416,600	410,500	946,400	1,107,500
Property, net	7,872,897	7,189,600	7,872,897	7,189,600	$ 7,436,430
Total assets	12,865,209	11,503,100	12,865,209	11,503,100	$ 11,526,742
Payment to acquire business, net of cash acquired	100,448		100,448
Corporate, other and eliminations
Financial information relating to segments
Net sales outside of segments	(19,000)	(20,300)	(53,400)	(67,200)
Cost of sales (exclusive of depreciation, amortization and depletion)	(48,100)	(42,400)	(67,900)	(53,100)
Selling, general and administrative	(2,300)	800	2,900	2,900
Depreciation, amortization and depletion	(100)	4,300	1,700	10,000
Exploration	4,700	7,900	13,900	22,800
Operating income	26,800	9,100	(4,000)	(49,800)
Capital investment	96,200	3,000	104,100	6,400
Property, net	58,000	127,500	58,000	127,500
Total assets	1,215,100	658,200	1,215,100	658,200
Corporate, other and eliminations | El Pilar
Financial information relating to segments
Payment to acquire business, net of cash acquired	100,400		100,400
Mexican Open-Pit | Operating segment
Financial information relating to segments
Net sales outside of segments	597,600	750,800	1,995,300	2,171,100
Cost of sales (exclusive of depreciation, amortization and depletion)	333,500	316,800	929,800	858,400
Selling, general and administrative	15,400	9,700	36,300	27,500
Depreciation, amortization and depletion	62,700	50,700	177,200	160,300
Exploration	3,400	800	5,200	2,500
Environmental remediation	7,000	37,200	23,500	37,200
Operating income	175,600	335,600	823,300	1,085,200
Capital investment	215,200	310,000	601,200	830,000
Property, net	4,824,700	4,149,600	4,824,700	4,149,600
Total assets	7,303,400	6,516,300	7,303,400	6,516,300
Mexican IMMSA Unit | Operating segment
Financial information relating to segments
Net sales outside of segments	68,400	75,700	245,800	259,200
Cost of sales (exclusive of depreciation, amortization and depletion)	80,300	78,300	247,800	245,700
Selling, general and administrative	1,500	4,100	4,900	11,700
Depreciation, amortization and depletion	9,000	8,700	24,600	24,300
Exploration	3,400	8,400	8,500	20,800
Operating income	(6,800)	(3,500)	13,400	23,900
Capital investment	14,000	12,600	29,400	30,800
Property, net	393,900	376,800	393,900	376,800
Total assets	815,800	877,600	815,800	877,600
Mexican IMMSA Unit | Intersegment sales
Financial information relating to segments
Net sales outside of segments	19,000	20,300	53,400	67,200
Peruvian Operations | Operating segment
Financial information relating to segments
Net sales outside of segments	467,600	648,100	1,550,200	1,886,100
Cost of sales (exclusive of depreciation, amortization and depletion)	305,100	376,800	947,700	1,047,000
Selling, general and administrative	9,000	11,700	29,300	34,100
Depreciation, amortization and depletion	60,000	50,200	170,400	145,800
Exploration	2,200	3,500	8,500	11,200
Operating income	91,300	205,900	394,300	648,000
Capital investment	91,200	84,900	211,700	240,300
Property, net	2,596,300	2,535,700	2,596,300	2,535,700
Total assets	$ 3,530,900	$ 3,451,000	$ 3,530,900	$ 3,451,000