REVENUE: - Revenue by Geographical Areas (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue Recognition
Net sales	$ 2,930.9	$ 2,505.6	$ 8,649.0	$ 7,600.2
Corporate, other and eliminations
Revenue Recognition
Net sales	(46.6)	(46.2)	(140.1)	(123.0)
Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	1,602.7	1,462.2	4,807.2	4,400.3
Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	184.9	153.6	516.6	474.3
Peruvian Operations | Operating segment
Revenue Recognition
Net sales	1,189.9	936.0	3,465.4	2,848.6
Mexico
Revenue Recognition
Net sales	795.9	789.1	2,212.0	2,165.4
Mexico | Corporate, other and eliminations
Revenue Recognition
Net sales	(44.9)	(36.6)	(119.2)	(105.5)
Mexico | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	694.0	712.6	1,939.9	1,902.9
Mexico | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	138.2	113.1	365.5	368.0
Mexico | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	8.6		25.8
United States
Revenue Recognition
Net sales	416.3	402.1	1,118.1	1,257.5
United States | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	281.1	257.4	878.7	851.9
United States | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	0.4		2.4	8.6
United States | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	134.8	144.7	237.0	397.0
Peru
Revenue Recognition
Net sales	169.0	113.1	502.9	386.4
Peru | Corporate, other and eliminations
Revenue Recognition
Net sales	(1.8)	(9.6)	(20.9)	(17.5)
Peru | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	1.7	9.6	20.7	17.4
Peru | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	169.0	113.1	503.2	386.5
Brazil
Revenue Recognition
Net sales	121.3	100.3	387.2	291.8
Brazil | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	8.2	9.3	30.2	24.7
Brazil | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	113.1	91.0	357.0	267.1
Chile
Revenue Recognition
Net sales	117.0	90.9	343.3	252.1
Chile | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales				(8.4)
Chile | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	117.0	90.9	343.3	260.5
Other American countries
Revenue Recognition
Net sales	18.2	18.8	50.2	54.6
Other American countries | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	11.6	13.1	32.3	33.3
Other American countries | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales				0.6
Other American countries | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	6.6	5.7	17.9	20.7
Switzerland
Revenue Recognition
Net sales	400.9	237.0	1,004.5	844.8
Switzerland | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	180.4	81.7	494.5	393.0
Switzerland | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	24.9	8.6	65.6	20.6
Switzerland | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	195.5	146.7	444.4	431.2
Italy
Revenue Recognition
Net sales	93.9	100.0	290.1	320.1
Italy | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales		0.5		0.7
Italy | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	7.6	3.6	20.1	13.1
Italy | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	86.3	95.9	270.0	306.3
Italy | Maximum
Revenue Recognition
Net sales	0.1		0.1
Spain
Revenue Recognition
Net sales	120.2	125.1	407.4	357.1
Spain | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	97.8	106.8	339.4	319.3
Spain | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	22.3	18.3	68.0	37.8
Other European Countries
Revenue Recognition
Net sales	168.7	106.3	501.1	288.0
Other European Countries | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	(1.6)	35.7	86.0	109.4
Other European Countries | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	3.7	5.7	9.1	16.5
Other European Countries | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	166.5	64.9	406.0	162.1
China
Revenue Recognition
Net sales	303.0	192.9	986.7	545.1
China | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	251.1	166.7	761.4	459.3
China | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	0.1	0.4	3.6	1.4
China | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	51.8	25.8	221.7	84.4
Singapore
Revenue Recognition
Net sales	48.5	112.7	182.1	330.8
Singapore | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	20.2	45.3	83.5	154.2
Singapore | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales		3.2	(0.6)	3.2
Singapore | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	28.4	64.2	99.3	173.4
Japan
Revenue Recognition
Net sales	143.1	89.5	570.6	420.9
Japan | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	57.1	15.5	138.4	107.6
Japan | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	86.0	74.0	432.2	313.3
Other Asian countries
Revenue Recognition
Net sales	15.0	27.8	92.7	85.6
Other Asian countries | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	10.9	26.9	53.0	77.1
Other Asian countries | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales		0.1		0.2
Other Asian countries | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	$ 4.1	$ 0.8	$ 39.7	$ 8.3