REVENUE: - Revenue by Geographical Areas (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue Recognition
Net sales	$ 2,599.8	$ 2,793.9
Corporate, other and eliminations
Revenue Recognition
Net sales	(41.3)	(38.2)
Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	1,466.0	1,626.9
Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	146.4	179.5
Peruvian Operations | Operating segment
Revenue Recognition
Net sales	1,028.7	1,025.7
Mexico
Revenue Recognition
Net sales	672.3	761.4
Mexico | Corporate, other and eliminations
Revenue Recognition
Net sales	(33.0)	(36.5)
Mexico | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	591.3	660.9
Mexico | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	106.2	137.0
Mexico | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	7.9
United States
Revenue Recognition
Net sales	312.6	512.4
United States | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	272.2	356.7
United States | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	1.7	7.4
United States | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	38.7	148.3
Peru
Revenue Recognition
Net sales	166.1	164.5
Peru | Corporate, other and eliminations
Revenue Recognition
Net sales	(8.3)	(1.7)
Peru | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	8.4	1.8
Peru | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	165.9	164.4
Brazil
Revenue Recognition
Net sales	124.9	108.1
Brazil | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	9.0	10.9
Brazil | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	116.0	97.2
Chile
Revenue Recognition
Net sales	94.4	100.7
Chile | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales		(5.2)
Chile | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	94.4	105.9
Other American countries
Revenue Recognition
Net sales	11.3	15.7
Other American countries | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	7.2	9.5
Other American countries | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	4.1	6.2
Switzerland
Revenue Recognition
Net sales	229.0	248.9
Switzerland | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	161.8	136.8
Switzerland | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	15.3	8.6
Switzerland | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	52.0	103.5
Italy
Revenue Recognition
Net sales	81.3	123.3
Italy | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales		(0.2)
Italy | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	6.0	6.4
Italy | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	75.3	117.1
Italy | Maximum
Revenue Recognition
Net sales	0.1
Spain
Revenue Recognition
Net sales	130.1	123.9
Spain | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	110.3	123.9
Spain | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	19.8
Other European Countries
Revenue Recognition
Net sales	166.8	120.2
Other European Countries | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	58.6	59.6
Other European Countries | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	1.4	7.3
Other European Countries | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	106.9	53.3
China
Revenue Recognition
Net sales	286.4	183.0
China | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	175.6	153.3
China | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	1.1
China | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	109.7	29.7
Singapore
Revenue Recognition
Net sales	57.3	101.5
Singapore | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	17.7	44.2
Singapore | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	(2.6)
Singapore | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	42.3	57.3
Japan
Revenue Recognition
Net sales	245.0	199.5
Japan | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	54.0	61.9
Japan | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	190.9	137.6
Other Asian countries
Revenue Recognition
Net sales	22.1	30.8
Other Asian countries | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	17.4	25.5
Other Asian countries | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales		0.1
Other Asian countries | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	$ 4.7	$ 5.2