REVENUE: - Revenue by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue Recognition
Net sales	$ 2,306.9	$ 2,897.0	$ 5,070.7	$ 5,429.5
Corporate, other and eliminations
Revenue Recognition
Net sales	(107.3)	(38.8)	(262.0)	(65.0)
Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	1,337.0	1,632.2	2,983.2	3,110.7
Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	166.3	161.4	343.8	285.7
Peruvian Operations | Operating segment
Revenue Recognition
Net sales	910.9	1,142.2	2,005.7	2,098.1
Copper
Revenue Recognition
Net sales	1,797.8	2,348.2	3,952.7	4,465.6
Copper | Corporate, other and eliminations
Revenue Recognition
Net sales	(82.1)	(19.2)	(211.9)	(32.9)
Copper | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	1,114.0	1,382.6	2,482.4	2,663.1
Copper | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	28.0	27.4	50.4	51.2
Copper | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	737.9	957.4	1,631.8	1,784.2
Molybdenum
Revenue Recognition
Net sales	198.2	282.2	474.0	451.8
Molybdenum | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	105.8	149.6	256.2	240.7
Molybdenum | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	92.4	132.6	217.8	211.1
Silver
Revenue Recognition
Net sales	99.4	81.3	204.6	117.0
Silver | Corporate, other and eliminations
Revenue Recognition
Net sales	(20.8)		(42.4)	0.5
Silver | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	58.1		124.8
Silver | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	36.8	81.3	73.8	116.5
Silver | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	25.3		48.4
Zinc
Revenue Recognition
Net sales	81.3	120.2	179.6	259.2
Zinc | Corporate, other and eliminations
Revenue Recognition
Net sales	(0.7)	(17.4)	(1.0)	(29.1)
Zinc | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales		68.0		140.7
Zinc | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	82.0	36.9	180.6	85.4
Zinc | Peruvian Operations | Operating segment
Revenue Recognition
Net sales		32.7		62.2
Other
Revenue Recognition
Net sales	130.2	65.1	259.8	135.9
Other | Corporate, other and eliminations
Revenue Recognition
Net sales	(3.7)	(2.2)	(6.7)	(3.5)
Other | Mexican Open-Pit | Operating segment
Revenue Recognition
Net sales	59.1	32.0	119.8	66.2
Other | Mexican IMMSA Unit | Operating segment
Revenue Recognition
Net sales	19.5	15.8	39.0	32.6
Other | Peruvian Operations | Operating segment
Revenue Recognition
Net sales	$ 55.3	$ 19.5	$ 107.7	$ 40.6