SEGMENT AND RELATED INFORMATION: - Financial (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) segment country item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Financial information related to segments
Number of reportable segments | segment									3
Number of countries having open-pit operations | country									2
Financial information relating to segments
Net sales (including sales to related parties, see note 16)	$ 1,694,700	$ 1,723,700	$ 1,837,200	$ 1,841,100	$ 1,864,300	$ 1,676,500	$ 1,529,800	$ 1,583,900	$ 7,096,700	$ 6,654,500	$ 5,379,800
Cost of sales (exclusive of depreciation, amortization and depletion)									3,409,000	3,252,800	3,034,100
Selling, general and administrative									102,600	93,100	94,300
Depreciation, amortization and depletion									674,300	671,100	647,100
Exploration									29,600	28,800	40,100
Environmental remediation										(10,200)
Operating income	623,600	696,700	787,600	773,300	830,000	692,600	525,900	570,400	2,881,200	2,618,900	1,564,200
Interest, net									(261,100)	(300,500)	(283,600)
Other income (expense)									(30,700)	(15,700)	(24,600)
Income taxes									(1,053,500)	(1,593,400)	(501,100)
Equity earnings of affiliate, net of income tax									12,300	23,100	23,900
Non-controlling interest									(5,200)	(3,900)	(2,300)
Net income attributable to SCC	293,300	$ 369,400	$ 409,600	$ 470,700	(287,400)	$ 401,800	$ 299,700	$ 314,400	1,543,000	728,500	776,500
Capital investment									1,121,400	1,023,500	1,118,500
Property and mine development, net	9,403,800				9,099,600				9,403,800	9,099,600	8,766,500
Total assets	14,484,800				13,780,100				14,484,800	13,780,100	13,234,300
Intersegment sales
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									(79,300)	(71,000)	(72,000)
Corporate, other and eliminations
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									(79,300)	(71,800)	(72,000)
Cost of sales (exclusive of depreciation, amortization and depletion)									(88,600)	(69,600)	(73,400)
Selling, general and administrative									2,100	1,100	2,300
Depreciation, amortization and depletion									28,900	10,300	15,500
Exploration									3,800	6,200	16,900
Operating income									(25,500)	(19,000)	(33,300)
Capital investment									20,600	4,000	4,700
Property and mine development, net	374,500				338,400				374,500	338,400	231,700
Total assets	576,300				253,400				$ 576,300	253,400	9,600
Mexican Open-pit
Financial information related to segments
Number of open-pit copper mines | item									2
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									$ 4,075,900	3,972,700	3,234,300
Mexican Open-pit | Operating segment
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									4,075,900	3,972,700	3,234,300
Cost of sales (exclusive of depreciation, amortization and depletion)									1,611,000	1,594,300	1,523,200
Selling, general and administrative									55,300	47,900	47,100
Depreciation, amortization and depletion									360,400	401,000	364,700
Exploration									2,000	2,700	5,200
Environmental remediation										(10,200)
Operating income									2,047,200	1,937,000	1,294,100
Capital investment									266,800	297,600	537,000
Property and mine development, net	4,783,800				5,004,500				4,783,800	5,004,500	5,136,800
Total assets	8,165,200				8,323,100				8,165,200	8,323,100	8,174,400
Mexican Open-pit | Reportable subsegments | Operating segment
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									$ 4,075,900	3,972,700	3,234,300
Mexican IMMSA Unit
Financial information related to segments
Number of underground poly metal mines | item									5
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									$ 527,900	509,500	423,100
Mexican IMMSA Unit | Operating segment
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									527,900	509,500	423,100
Cost of sales (exclusive of depreciation, amortization and depletion)									377,200	365,300	304,100
Selling, general and administrative									8,500	7,900	7,400
Depreciation, amortization and depletion									47,600	56,200	49,800
Exploration									5,300	5,500	5,000
Operating income									89,300	73,800	56,800
Capital investment									60,000	36,500	35,800
Property and mine development, net	448,300				366,900				448,300	366,900	448,700
Total assets	930,200				889,100				930,200	889,100	825,000
Mexican IMMSA Unit | Reportable subsegments | Operating segment
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									448,600	437,700	351,100
Mexican IMMSA Unit | Intersubsegment sales | Operating segment
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									$ 79,300	71,000	72,000
Peruvian Operations
Financial information related to segments
Number of open-pit copper mines | item									2
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									$ 2,572,200	2,244,100	1,794,400
Peruvian Operations | Operating segment
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									2,572,200	2,244,100	1,794,400
Cost of sales (exclusive of depreciation, amortization and depletion)									1,509,400	1,362,800	1,280,200
Selling, general and administrative									36,700	36,200	37,500
Depreciation, amortization and depletion									237,400	203,600	217,100
Exploration									18,500	14,400	13,000
Operating income									770,200	627,100	246,600
Capital investment									774,000	685,400	541,000
Property and mine development, net	3,797,200				3,389,800				3,797,200	3,389,800	2,949,300
Total assets	$ 4,813,100				$ 4,314,500				4,813,100	4,314,500	4,225,300
Peruvian Operations | Reportable subsegments | Operating segment
Financial information relating to segments
Net sales (including sales to related parties, see note 16)									$ 2,572,200	$ 2,244,100	$ 1,794,400