SEGMENT AND RELATED INFORMATION: (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) segment	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Financial information related to segments
Number of reportable segments | segment			3
Financial information relating to segments
Net sales	$ 2,930.9	$ 2,505.6	$ 8,649.0	$ 7,600.2
Cost of sales (exclusive of depreciation, amortization and depletion)	1,223.1	1,175.7	3,629.6	3,517.6
Selling, general and administrative	31.2	32.7	96.0	94.1
Depreciation, amortization and depletion	213.1	212.5	631.7	625.4
Exploration	13.2	15.5	44.4	39.5
Operating income	1,450.3	1,069.2	4,247.3	3,323.6
Interest, net	(44.8)	(60.7)	(154.7)	(180.5)
Other income (expense)	21.2	8.9	20.3	24.9
Income taxes	(526.4)	(395.3)	(1,528.6)	(1,170.2)
Equity earnings of affiliate	(0.5)	(0.1)	8.1	(10.3)
Non-controlling interest	(3.1)	(2.5)	(9.5)	(7.3)
Net income attributable to SCC	896.7	619.5	2,582.9	1,980.2
Capital investment	246.4	262.7	792.0	753.2
Property and mine development, net	9,927.1	9,730.8	9,927.1	9,730.8	$ 9,782.9
Total assets	18,415.5	16,965.0	18,415.5	16,965.0	$ 16,725.3
Corporate, other and eliminations
Financial information relating to segments
Net sales	(46.6)	(46.2)	(140.1)	(123.0)
Cost of sales (exclusive of depreciation, amortization and depletion)	(56.8)	(40.1)	(148.3)	(118.5)
Selling, general and administrative	1.8	1.8	6.4	6.6
Depreciation, amortization and depletion	8.5	10.2	26.2	32.7
Exploration	2.0	3.4	6.4	8.7
Operating income	(2.2)	(21.5)	(30.9)	(52.5)
Capital investment	3.7	5.0	10.0	11.8
Property and mine development, net	513.1	752.9	513.1	752.9
Total assets	2,770.0	2,636.5	2,770.0	2,636.5
Reportable subsegments
Financial information relating to segments
Net sales	2,930.9	2,505.6	8,649.0	7,600.2
Intersegment sales | Corporate, other and eliminations
Financial information relating to segments
Net sales	(46.6)	(46.2)	(140.1)	(123.0)
Mexican Open-Pit | Operating segment
Financial information relating to segments
Net sales	1,602.7	1,462.2	4,807.2	4,400.3
Cost of sales (exclusive of depreciation, amortization and depletion)	612.7	591.6	1,870.3	1,781.9
Selling, general and administrative	17.1	18.9	52.3	51.7
Depreciation, amortization and depletion	105.4	96.9	307.7	288.1
Exploration	1.3	1.9	7.3	4.6
Operating income	866.2	752.9	2,569.6	2,274.0
Capital investment	145.2	141.5	486.9	406.3
Property and mine development, net	4,852.6	4,634.3	4,852.6	4,634.3
Total assets	8,975.0	8,531.7	8,975.0	8,531.7
Mexican Open-Pit | Reportable subsegments | Operating segment
Financial information relating to segments
Net sales	1,596.7	1,462.2	4,801.1	4,400.3
Mexican Open-Pit | Intersegment sales | Operating segment
Financial information relating to segments
Net sales	6.0		6.0
Mexican IMMSA Unit | Operating segment
Financial information relating to segments
Net sales	184.9	153.6	516.6	474.3
Cost of sales (exclusive of depreciation, amortization and depletion)	123.2	133.3	362.8	411.5
Selling, general and administrative	3.2	2.6	9.1	7.9
Depreciation, amortization and depletion	19.3	16.8	56.7	51.6
Exploration	2.6	2.1	7.0	6.0
Operating income	36.6	(1.2)	80.9	(2.7)
Capital investment	30.2	40.1	91.5	102.6
Property and mine development, net	784.9	727.4	784.9	727.4
Total assets	1,196.6	1,153.6	1,196.6	1,153.6
Mexican IMMSA Unit | Reportable subsegments | Operating segment
Financial information relating to segments
Net sales	144.3	107.4	382.5	351.3
Mexican IMMSA Unit | Intersegment sales | Operating segment
Financial information relating to segments
Net sales	40.6	46.2	134.0	123.0
Peruvian Operations | Operating segment
Financial information relating to segments
Net sales	1,189.9	936.0	3,465.4	2,848.6
Cost of sales (exclusive of depreciation, amortization and depletion)	543.9	490.9	1,544.6	1,442.7
Selling, general and administrative	9.1	9.4	28.2	27.9
Depreciation, amortization and depletion	79.9	88.6	241.1	253.0
Exploration	7.3	8.1	23.8	20.2
Operating income	549.7	339.0	1,627.6	1,104.8
Capital investment	67.2	76.1	203.6	232.5
Property and mine development, net	3,776.5	3,616.2	3,776.5	3,616.2
Total assets	5,473.9	4,643.2	5,473.9	4,643.2
Peruvian Operations | Reportable subsegments | Operating segment
Financial information relating to segments
Net sales	$ 1,189.9	$ 936.0	$ 3,465.3	$ 2,848.6