RELATED PARTY TRANSACTIONS: (Details) $ in Millions	3 Months Ended		12 Months Ended
RELATED PARTY TRANSACTIONS: (Details) $ in Millions	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2020 MWh	Dec. 31, 2012 item MW	Dec. 31, 2025 USD ($)	Dec. 31, 2014 item
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	$ 11.9				$ 16.2
Affiliates
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	11.9				16.2
Related parties payable:	133.4				138.4
Total purchases	93.8	$ 106.2
Total sales	$ 0.9	0.8
Affiliates \| Compaia Minera Coimolache S.A. ("Coimolache")
RELATED PARTY TRANSACTIONS:
Ownership percentage (Equity method investment)	44.20%
Affiliates \| Apu Coropuna S.R.L.
RELATED PARTY TRANSACTIONS:
Ownership percentage (Equity method investment)	30.00%
Affiliates \| Minimum
RELATED PARTY TRANSACTIONS:
Aggregate consideration of Material Affiliate Transaction to be be authorized by the General Counsel and CFO	$ 8.0
Affiliates \| Maximum
RELATED PARTY TRANSACTIONS:
Aggregate consideration of Material Affiliate Transaction to be be authorized by the General Counsel and CFO	10.0
Grupo Mexico and affiliates \| Affiliates
RELATED PARTY TRANSACTIONS:
Total sales	19.8	31.4
Asarco LLC ("Asarco") \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	7.8				7.1
Related parties payable:	52.7				61.1
Total purchases	1.2	7.8
Total sales	13.0	13.0
AMMINCO Apoyo Administrativo, S.A. de C.V. ("AMMINCO") \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	15.8				15.9
Total purchases	3.0	2.5
Eolica El Retiro, S.A.P.I. de C.V.
RELATED PARTY TRANSACTIONS:
Number of wind turbines \| item						37
Eolica El Retiro, S.A.P.I. de C.V. \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	0.4				0.3
Total purchases	$ 0.1	$ 0.4
Percentage of supply to third-party energy users	17.10%	33.30%
Ferrocarril Mexicano, S.A. de C.V. \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	$ 7.5				4.0
Total purchases	6.8	$ 5.5
Grupo Mexico and affiliates \| Affiliates
RELATED PARTY TRANSACTIONS:
Total purchases	0.8	1.0
Grupo Mexico Servicios \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	3.1				3.3
Total purchases	5.4	5.0
Mexico Generadora de Energia S. de R.L. ("MGE") \| Mexico
RELATED PARTY TRANSACTIONS:
Number of natural gas-fired combined cycle power generating units \| item				2
Mexico Generadora de Energia S. de R.L. ("MGE") \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	2.0				7.6
Related parties payable:	32.1				30.2
Total purchases	51.3	59.7
Total sales	$ 6.8	$ 18.4
Mexico Generadora de Energia S. de R.L. ("MGE") \| Affiliates \| Mexico
RELATED PARTY TRANSACTIONS:
Net total capacity (in megawatts) \| MW				516.2
Percentage of supply to third-party energy users	15.10%	3.70%
Mexico Compania Constructora S.A de C.V. \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	$ 8.6				12.4
Total purchases	9.5	$ 14.2
Parque Eolico de Fenicias, S. de R.L. de C.V. \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	8.0				7.5
Total purchases	$ 10.7	$ 8.6
Percentage of supply to third-party energy users	88.10%	74.80%
Purchase agreement, contracted power capacity (in megawatts per year) \| MWh			611,400
Term of power purchase agreement related to sale of power plant			20 years
Grupo Mexico Servicios de Ingenieria, S.A. de C.V. \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	$ 3.7				2.3
Total purchases	5.8	$ 2.3
AMMINCO, Ferrocarril Mexicano, S.A. de C.V. & Mexico Compania Constructora S.A de C.V. \| Affiliates \| Maximum
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	0.1				0.1
AMMINCO & Ferrocarril Mexicano, S.A. de C.V. \| Affiliates \| Maximum
RELATED PARTY TRANSACTIONS:
Threshold revenue from related parties	0.1	0.1
Boutique Bowling de Mexico, S.A. de C.V. \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties payable:	0.9				0.8
Total purchases	0.1	0.1
Empresarios Industriales de Mexico, S.A. de C.V \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	1.7				1.5
Total sales	0.2	0.1
Mextransport \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	0.2
Related parties payable:	0.4				0.4
Total purchases	0.6	0.8
Total sales	0.6	0.7
Operadora de Cinemas S.A. de C.V. \| Affiliates
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	0.1				0.1
Related parties payable:	0.4				$ 0.3
Total purchases	$ 0.1	$ 0.1

SOUTHERN COPPER CORP/ 10-Q