REVENUE: - Revenue by Geographical Areas (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenue Recognition
Net sales	$ 2,505.6	$ 2,156.9	$ 7,600.2	$ 7,227.6
Corporate, other and eliminations
Revenue Recognition
Net sales	(46.2)	(19.5)	(123.0)	(281.5)
Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	1,462.2	1,201.5	4,400.3	4,184.7
Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	153.6	159.2	474.3	503.0
Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	936.0	815.7	2,848.6	2,821.4
Mexico
Revenue Recognition
Net sales	789.1	487.6	2,165.4	1,632.7
Mexico \| Corporate, other and eliminations
Revenue Recognition
Net sales	(36.6)	(30.9)	(105.5)	(114.9)
Mexico \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	712.6	414.7	1,902.9	1,390.8
Mexico \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	113.1	103.8	368.0	356.8
United States
Revenue Recognition
Net sales	402.1	431.7	1,257.5	1,557.3
United States \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	257.4	333.9	851.9	1,237.2
United States \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales		11.4	8.6	37.8
United States \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	144.7	86.4	397.0	282.3
Peru
Revenue Recognition
Net sales	113.1	118.3	386.4	451.6
Peru \| Corporate, other and eliminations
Revenue Recognition
Net sales	(9.6)	11.4	(17.5)	(166.6)
Peru \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales		(19.7)		158.6
Peru \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	9.6		17.4
Peru \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	113.1	126.6	386.5	459.6
Brazil
Revenue Recognition
Net sales	100.3	120.6	291.8	345.0
Brazil \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	9.3	16.1	24.7	25.7
Brazil \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	91.0	104.5	267.1	319.3
Chile
Revenue Recognition
Net sales	90.9	101.6	252.1	287.1
Chile \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales		10.4	(8.4)	10.9
Chile \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	90.9	91.2	260.5	276.2
Other American countries
Revenue Recognition
Net sales	18.8	19.7	54.6	53.0
Other American countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	13.1	10.8	33.3	28.5
Other American countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales		1.2	0.6	2.2
Other American countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	5.7	7.7	20.7	22.3
Switzerland
Revenue Recognition
Net sales	237.0	296.4	844.8	1,001.8
Switzerland \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	81.7	123.9	393.0	450.2
Switzerland \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	8.6	10.9	20.6	33.8
Switzerland \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	146.7	161.6	431.2	517.8
Italy
Revenue Recognition
Net sales	100.0	80.5	320.1	211.7
Italy \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	0.5		0.7	1.3
Italy \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	3.6	6.2	13.1	13.9
Italy \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	95.9	74.3	306.3	196.5
Spain
Revenue Recognition
Net sales	125.1	87.2	357.1	327.3
Spain \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	106.8	90.2	319.3	290.5
Spain \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	18.3	(3.0)	37.8	36.8
Other European Countries
Revenue Recognition
Net sales	106.3	101.5	288.0	258.0
Other European Countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	35.7	49.0	109.4	90.9
Other European Countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	5.7	9.6	16.5	24.0
Other European Countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	64.9	42.9	162.1	143.1
China
Revenue Recognition
Net sales	192.9	120.0	545.1	326.9
China \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	166.7	101.9	459.3	308.8
China \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	0.4		1.4
China \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	25.8	18.1	84.4	18.1
Singapore
Revenue Recognition
Net sales	112.7	62.1	330.8	161.0
Singapore \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	45.3	48.1	154.2	53.5
Singapore \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	3.2	(0.1)	3.2	8.4
Singapore \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	64.2	14.1	173.4	99.1
Japan
Revenue Recognition
Net sales	89.5	93.8	420.9	431.4
Japan \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	15.5	9.2	107.6	51.8
Japan \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	74.0	84.6	313.3	379.6
Other Asian countries
Revenue Recognition
Net sales	27.8	35.9	85.6	182.8
Other Asian countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	26.9	29.1	77.1	111.7
Other Asian countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	0.1	0.1	0.2	0.4
Other Asian countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	$ 0.8	$ 6.7	$ 8.3	$ 70.7