REVENUE: - Revenue by Geographical Areas (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenue Recognition
Net sales	$ 3,118.3	$ 2,300.7	$ 5,718.1	$ 5,094.6
Corporate, other and eliminations
Revenue Recognition
Net sales	(52.1)	(38.6)	(93.4)	(76.8)
Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	1,738.5	1,311.2	3,204.4	2,938.1
Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	185.2	141.2	331.6	320.7
Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	1,246.7	886.9	2,275.4	1,912.6
Mexico
Revenue Recognition
Net sales	743.8	615.0	1,416.1	1,376.4
Mexico \| Corporate, other and eliminations
Revenue Recognition
Net sales	(41.3)	(32.4)	(74.3)	(68.9)
Mexico \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	654.7	529.5	1,246.0	1,190.4
Mexico \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	121.0	117.9	227.2	254.9
Mexico \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	9.3		17.2
United States
Revenue Recognition
Net sales	389.2	343.2	701.8	855.5
United States \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	325.4	237.8	597.6	594.5
United States \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	0.3	1.3	2.0	8.6
United States \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	63.5	104.1	102.2	252.4
Peru
Revenue Recognition
Net sales	167.9	108.9	334.0	273.3
Peru \| Corporate, other and eliminations
Revenue Recognition
Net sales	(10.8)	(6.2)	(19.1)	(7.9)
Peru \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	10.6	6.1	19.0	7.8
Peru \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	168.2	109.0	334.1	273.4
Brazil
Revenue Recognition
Net sales	141.0	83.3	265.9	191.4
Brazil \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	13.1	4.4	22.0	15.3
Brazil \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	127.9	78.9	243.9	176.1
Chile
Revenue Recognition
Net sales	131.9	60.5	226.4	161.3
Chile \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales		(3.2)		(8.4)
Chile \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	131.9	63.7	226.4	169.7
Other American countries
Revenue Recognition
Net sales	20.7	20.0	32.0	35.8
Other American countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	13.5	10.7	20.7	20.2
Other American countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales		0.5		0.6
Other American countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	7.2	8.8	11.3	15.0
Switzerland
Revenue Recognition
Net sales	374.6	358.9	603.6	607.8
Switzerland \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	152.3	174.5	314.1	311.3
Switzerland \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	25.4	3.4	40.7	12.0
Switzerland \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	196.9	181.0	248.9	284.5
Italy
Revenue Recognition
Net sales	114.8	96.8	196.1	220.1
Italy \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales		0.4		0.2
Italy \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	6.4	3.1	12.5	9.5
Italy \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	108.4	93.3	183.7	210.4
Italy \| Maximum
Revenue Recognition
Net sales	0.1		0.1
Spain
Revenue Recognition
Net sales	157.1	108.0	287.2	231.9
Spain \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	131.3	88.6	241.6	212.5
Spain \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	25.8	19.4	45.7	19.4
Other European Countries
Revenue Recognition
Net sales	165.6	61.4	332.4	181.7
Other European Countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	29.0	14.1	87.6	73.7
Other European Countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	4.0	3.4	5.4	10.8
Other European Countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	132.5	43.9	239.4	97.2
China
Revenue Recognition
Net sales	397.3	169.2	683.7	352.2
China \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	334.7	139.3	510.3	292.6
China \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	2.4	1.0	3.5	1.0
China \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	60.2	28.9	169.9	58.6
Singapore
Revenue Recognition
Net sales	76.3	116.6	133.6	218.0
Singapore \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	45.7	64.7	63.3	108.8
Singapore \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	2.0		(0.6)
Singapore \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	28.6	51.9	70.9	109.2
Japan
Revenue Recognition
Net sales	182.5	131.8	427.5	331.3
Japan \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	27.2	30.1	81.3	92.0
Japan \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	155.3	101.7	346.2	239.3
Other Asian countries
Revenue Recognition
Net sales	55.6	27.1	77.7	57.9
Other Asian countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	24.7	24.7	42.0	50.3
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	$ 30.9	$ 2.3	$ 35.6	$ 7.4