INCOME TAXES: - Tax assets and liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Assets:
Inventories	$ 57.2	$ 52.4
Capitalized exploration expenses	19.2	15.6
U.S. foreign tax credit carryforward, net of Uncertain Tax Positions	2,171.3	1,904.1
U.S. tax effect of Peruvian deferred tax liability	85.7	83.5
U.S. tax effect of Peruvian Uncertain Tax Positions	59.6	69.6
Reserves	284.3	315.4
Deferred workers participation	12.2	12.2
Accrued salaries, wages and vacations	8.4	7.7
Sales price adjustment (PUI)	4.2	(0.3)
Deferred charges	106.8
Valuation allowance on U.S. deferred tax assets, foreign tax credits and U.S. tax effect of Peruvian deferred	(2,545.9)	(2,301.7)
Accrued royalty and special mining tax	14.1	29.6
Other	11.3	16.5
Total deferred tax assets	288.4	204.6
Liabilities:
Property, plant and equipment	(92.0)	(68.1)
Social responsibility expenses	(10.3)	(9.7)
Other		(2.9)
Total deferred tax liabilities	(102.3)	(80.7)
Total net deferred tax (liabilities) / assets	186.1	$ 123.9
Increase in valuation allowance	$ 244.2