REVENUE: - Revenue by Geographical Areas (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenue Recognition
Net sales	$ 2,300.7	$ 2,306.9	$ 5,094.6	$ 5,070.7
Corporate, other and eliminations
Revenue Recognition
Net sales	(38.6)	(107.3)	(76.8)	(262.0)
Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	1,311.2	1,337.0	2,938.1	2,983.2
Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	141.2	166.3	320.7	343.8
Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	886.9	910.9	1,912.6	2,005.7
Mexico
Revenue Recognition
Net sales	615.0	520.6	1,376.4	1,145.2
Mexico \| Corporate, other and eliminations
Revenue Recognition
Net sales	(32.4)	(44.0)	(68.9)	(84.0)
Mexico \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	529.5	442.2	1,190.4	976.0
Mexico \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	117.9	122.4	254.9	253.2
United States
Revenue Recognition
Net sales	343.2	563.6	855.5	1,125.7
United States \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	237.8	447.7	594.5	903.3
United States \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	1.3	10.7	8.6	26.4
United States \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	104.1	105.2	252.4	196.0
Peru
Revenue Recognition
Net sales	108.9	155.5	273.3	333.4
Peru \| Corporate, other and eliminations
Revenue Recognition
Net sales	(6.2)	(63.3)	(8.0)	(178.0)
Peru \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales		63.3		178.4
Peru \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	6.1		7.8
Peru \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	109.0	155.5	273.4	333.0
Brazil
Revenue Recognition
Net sales	83.3	100.3	191.4	224.4
Brazil \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	4.4	4.5	15.3	9.6
Brazil \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	78.9	95.8	176.1	214.8
Chile
Revenue Recognition
Net sales	60.5	82.1	161.3	185.6
Chile \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	(3.2)	0.6	(8.4)	0.6
Chile \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	63.7	81.5	169.7	185.0
Other American countries
Revenue Recognition
Net sales	20.0	21.2	35.8	33.1
Other American countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	10.7	11.2	20.2	17.7
Other American countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	0.5	0.7	0.6	0.7
Other American countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	8.8	9.3	15.0	14.7
Switzerland
Revenue Recognition
Net sales	358.9	278.4	607.8	705.3
Switzerland \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	174.5	98.8	311.3	326.2
Switzerland \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	3.4	14.5	12.0	22.9
Switzerland \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	181.0	165.1	284.5	356.2
Italy
Revenue Recognition
Net sales	96.8	59.3	220.1	131.3
Italy \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	0.4	0.8	0.2	1.3
Italy \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	3.1	3.8	9.5	7.8
Italy \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	93.3	54.7	210.4	122.2
Spain
Revenue Recognition
Net sales	108.0	145.1	231.9	240.0
Spain \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	88.6	107.1	212.5	200.3
Spain \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	19.4	38.0	19.4	39.7
Other European Countries
Revenue Recognition
Net sales	61.4	31.1	181.7	156.4
Other European Countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	14.1	11.1	73.7	41.9
Other European Countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	3.4	6.0	10.8	14.4
Other European Countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	43.9	14.0	97.2	100.1
China
Revenue Recognition
Net sales	169.2	94.5	352.2	206.9
China \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	139.3	94.5	292.6	206.9
China \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	1.0		1.0
China \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	28.9		58.6
Singapore
Revenue Recognition
Net sales	116.6	37.1	218.0	98.9
Singapore \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	64.7	0.7	108.8	5.4
Singapore \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales		3.6		8.5
Singapore \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	51.9	32.8	109.2	85.0
Japan
Revenue Recognition
Net sales	131.8	154.1	331.3	337.6
Japan \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	30.1	20.6	92.0	42.6
Japan \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	101.7	133.5	239.3	295.0
Other Asian countries
Revenue Recognition
Net sales	27.1	64.0	57.9	146.9
Other Asian countries \| Mexican Open-Pit \| Operating segment
Revenue Recognition
Net sales	24.7	38.4	50.3	82.6
Other Asian countries \| Mexican IMMSA Unit \| Operating segment
Revenue Recognition
Net sales	0.1	0.1	0.2	0.3
Other Asian countries \| Peruvian Operations \| Operating segment
Revenue Recognition
Net sales	$ 2.3	$ 25.5	$ 7.4	$ 64.0