REVENUE: - Revenue by Geographical Areas (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
REVENUE:
Net sales	$ 4,289.0	$ 3,051.0	$ 8,540.4	$ 6,172.9
Operating segment
REVENUE:
Net sales	4,364.3	3,112.3	8,707.7	6,283.1
Corporate & Elimination
REVENUE:
Net sales	(75.4)	(61.3)	(167.3)	(110.2)
Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	2,511.9	1,754.8	4,955.5	3,504.2
Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales	267.9	179.3	586.5	334.7
Peruvian Operations \| Operating segment
REVENUE:
Net sales	1,584.4	1,178.2	3,165.8	2,444.2
Mexico
REVENUE:
Net sales	1,141.2	804.7	2,222.4	1,617.8
Mexico \| Operating segment
REVENUE:
Net sales	1,216.5	865.7	2,389.8	1,727.1
Mexico \| Corporate & Elimination
REVENUE:
Net sales	(75.4)	(61.0)	(167.3)	(109.3)
Mexico \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	1,010.6	714.7	1,945.2	1,439.9
Mexico \| Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales	206.0	151.1	444.5	287.0
Mexico \| Peruvian Operations \| Operating segment
REVENUE:
Net sales				0.2
United States
REVENUE:
Net sales	579.4	356.0	1,164.1	765.1
United States \| Operating segment
REVENUE:
Net sales	579.4	356.0	1,164.1	765.1
United States \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	269.0	277.6	560.4	563.6
United States \| Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales	4.0	0.2	8.2	0.2
United States \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	306.4	78.2	595.6	201.3
Peru
REVENUE:
Net sales	340.9	212.9	633.4	437.8
Peru \| Operating segment
REVENUE:
Net sales	340.9	213.2	633.4	438.7
Peru \| Corporate & Elimination
REVENUE:
Net sales		(0.2)		(0.9)
Peru \| Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales		(0.2)		1.0
Peru \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	340.9	213.4	633.4	437.8
Brazil
REVENUE:
Net sales	190.7	162.1	412.6	299.5
Brazil \| Operating segment
REVENUE:
Net sales	190.7	162.1	412.6	299.5
Brazil \| Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales	5.6	8.3	15.1	15.5
Brazil \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	185.1	153.9	397.5	283.9
Chile
REVENUE:
Net sales	174.5	132.1	355.8	241.7
Chile \| Operating segment
REVENUE:
Net sales	174.5	132.1	355.8	241.7
Chile \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	174.5	132.1	355.8	241.7
Other American countries
REVENUE:
Net sales	30.3	18.8	51.1	32.4
Other American countries \| Operating segment
REVENUE:
Net sales	30.3	18.8	51.1	32.4
Other American countries \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	15.6	10.8	31.3	22.4
Other American countries \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	14.7	8.0	19.8	10.0
Switzerland
REVENUE:
Net sales	433.4	424.2	905.7	817.9
Switzerland \| Operating segment
REVENUE:
Net sales	433.4	424.2	905.7	817.9
Switzerland \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	255.5	221.6	507.5	441.3
Switzerland \| Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales	36.4	15.1	78.5	20.7
Switzerland \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	141.5	187.5	319.6	355.9
Italy
REVENUE:
Net sales	161.4	112.8	290.0	218.2
Italy \| Operating segment
REVENUE:
Net sales	161.4	112.8	290.0	218.2
Italy \| Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales	2.9	3.8	8.7	9.1
Italy \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	158.5	109.0	281.2	209.1
Spain
REVENUE:
Net sales	251.5	163.1	456.1	322.8
Spain \| Operating segment
REVENUE:
Net sales	251.5	163.1	456.1	322.8
Spain \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	210.6	136.6	374.4	245.3
Spain \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	40.9	26.5	81.7	77.5
Other European countries
REVENUE:
Net sales	294.7	81.7	725.2	271.7
Other European countries \| Operating segment
REVENUE:
Net sales	294.7	81.7	725.2	271.7
Other European countries \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	201.9	0.7	489.2	3.7
Other European countries \| Mexican IMMSA Unit \| Operating segment
REVENUE:
Net sales	13.0	1.1	31.5	1.2
Other European countries \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	79.8	79.9	204.6	266.7
China
REVENUE:
Net sales	314.7	232.8	645.4	516.4
China \| Operating segment
REVENUE:
Net sales	314.7	232.8	645.4	516.4
China \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	302.2	225.2	611.6	504.9
China \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	12.6	7.6	33.8	11.5
Singapore
REVENUE:
Net sales	4.3	48.2	37.2	91.2
Singapore \| Operating segment
REVENUE:
Net sales	4.3	48.2	37.2	91.2
Singapore \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	(0.2)	22.5	30.6	41.7
Singapore \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	4.5	25.7	6.6	49.5
Japan
REVENUE:
Net sales	333.5	272.0	551.8	487.5
Japan \| Operating segment
REVENUE:
Net sales	333.5	272.0	551.8	487.5
Japan \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	218.7	125.5	334.8	207.2
Japan \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	114.8	146.4	217.0	280.3
Other Asian countries
REVENUE:
Net sales	38.5	29.6	89.7	53.1
Other Asian countries \| Operating segment
REVENUE:
Net sales	38.5	29.6	89.7	53.1
Other Asian countries \| Mexican Open-Pit \| Operating segment
REVENUE:
Net sales	28.2	19.5	70.6	34.2
Other Asian countries \| Peruvian Operations \| Operating segment
REVENUE:
Net sales	$ 10.2	$ 10.1	$ 19.1	$ 19.0