INCOME TAXES: (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Taxes
Statutory income tax provision			$ 972.7	$ 1,387.0
Peruvian royalty			24.7	70.1
Mexican royalty			97.9	162.5
Peruvian special mining tax			41.7	84.2
Total income tax provision	$ 228.5	$ 548.6	$ 1,137.0	$ 1,703.8
Effective income tax rate (as a percent)			39.50%	40.00%
Peru
Income Taxes
Increase (Decrease) in Income tax expense (benefit)			$ 58.0
Royalty charges			66.4	$ 154.3
Mexico
Income Taxes
Mexican royalty			$ 97.9	$ 162.5