RELATED PARTY TRANSACTIONS: (Details)	3 Months Ended						3 Months Ended					0 Months Ended	3 Months Ended			3 Months Ended			3 Months Ended		12 Months Ended		12 Months Ended				3 Months Ended			3 Months Ended				3 Months Ended	12 Months Ended	3 Months Ended			3 Months Ended									3 Months Ended
	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)	Mar. 31, 2012 Minera Mexico Maximum	Mar. 31, 2013 Grupo Mexico, S.A.B de C.V. ( Grupo Mexico ) and affiliates USD ($)	Dec. 31, 2012 Grupo Mexico, S.A.B de C.V. ( Grupo Mexico ) and affiliates USD ($)	Mar. 31, 2013 Asarco LLC ("Asarco") USD ($)	Mar. 31, 2012 Asarco LLC ("Asarco") USD ($)	Dec. 31, 2012 Asarco LLC ("Asarco") USD ($)	Mar. 31, 2013 Compania Perforadora Mexico S.A.P.I. de C.V. USD ($)	Dec. 31, 2012 Compania Perforadora Mexico S.A.P.I. de C.V. USD ($)	Apr. 02, 2013 Compania Minera Coimolache S.A. USD ($)	Mar. 31, 2013 Compania Minera Coimolache S.A. USD ($)	Mar. 31, 2012 Compania Minera Coimolache S.A. USD ($)	Dec. 31, 2012 Compania Minera Coimolache S.A. USD ($)	Mar. 31, 2013 Mexico Proyectos y Desarrollos, S.A. de C.V. and affiliates USD ($)	Mar. 31, 2012 Mexico Proyectos y Desarrollos, S.A. de C.V. and affiliates USD ($)	Dec. 31, 2012 Mexico Proyectos y Desarrollos, S.A. de C.V. and affiliates USD ($)	Mar. 31, 2013 MGE USD ($)	Mar. 31, 2012 MGE USD ($)	Dec. 31, 2005 MGE item	May 31, 2010 MGE USD ($)	Dec. 31, 2012 MGE Line of credit USD ($)	Dec. 31, 2011 MGE Line of credit USD ($)	Mar. 31, 2012 MGE Controladora de Infraestructura Energetica Mexico, S. A. de C. V. USD ($)	Mar. 31, 2012 MGE Controladora de Infraestructura Energetica Mexico, S. A. de C. V. MXN	Mar. 31, 2013 Higher Technology S.A.C. USD ($)	Mar. 31, 2012 Higher Technology S.A.C. USD ($)	Dec. 31, 2012 Higher Technology S.A.C. USD ($)	Mar. 31, 2013 Breaker, S.A. de C.V USD ($)	Mar. 31, 2012 Breaker, S.A. de C.V USD ($)	Mar. 31, 2013 Mexico Transportes Aereos S.A. de C.V. ("Mextransport") USD ($)	Dec. 31, 2012 Mexico Transportes Aereos S.A. de C.V. ("Mextransport") USD ($)	Mar. 31, 2013 Mexico Transportes Aereos S.A. de C.V. ("Mextransport") Mexican subsidiaries USD ($)	Dec. 31, 2007 Mexico Transportes Aereos S.A. de C.V. ("Mextransport") Mexican subsidiaries item	Mar. 31, 2013 Ferrocarril Mexicano, S.A. de C.V. USD ($)	Mar. 31, 2012 Ferrocarril Mexicano, S.A. de C.V. USD ($)	Dec. 31, 2012 Ferrocarril Mexicano, S.A. de C.V. USD ($)	Mar. 31, 2013 Cia Perforadora Mexico S.A.P.I. de C.V and affiliates USD ($)	Mar. 31, 2012 Cia Perforadora Mexico S.A.P.I. de C.V and affiliates USD ($)	Mar. 31, 2013 Mextransport USD ($)	Mar. 31, 2012 Mextransport USD ($)	Mar. 31, 2013 Servicios y Fabricaciones Mecanicas S.A.C. USD ($)	Mar. 31, 2013 Sempertrans France Belting Technology USD ($)	Mar. 31, 2013 Grupo Mexico item	Mar. 31, 2013 Mexico Generadora de Energia S.de R.L. ("MGE") USD ($)	Dec. 31, 2012 Mexico Generadora de Energia S.de R.L. ("MGE") USD ($)	Mar. 31, 2013 Grupo Mexico Servicios S.A de C.V USD ($)	Mar. 31, 2012 Grupo Mexico Servicios S.A de C.V USD ($)
RELATED PARTY TRANSACTIONS:
Related parties receivable current:	$ 34,165,000		$ 25,740,000		$ 800,000	$ 1,800,000	$ 9,200,000			$ 600,000	$ 500,000		$ 23,400,000		$ 23,400,000	$ 200,000
Related parties receivable non-current:	173,377,000		183,950,000																																											173,400,000	184,000,000
Related parties payable:	4,100,000		20,300,000		700,000				15,300,000									2,100,000									100,000		200,000	300,000		400,000	100,000			2,600,000		2,600,000
Total purchases from related parties	54,000,000	26,000,000					32,900,000	5,600,000								9,300,000	11,200,000										300,000	300,000		800,000	500,000					5,800,000	4,100,000		600,000	100,000	600,000	700,000	100,000	100,000				3,500,000	3,500,000
Sales and total other revenues from related parties	37,100,000	11,800,000
Number of power plants																					2
Line of credit																						350,000,000
Interest rate (as a percent)													3.45%							5.75%
Ownership percentage				0.001%									44.20%												99.999%	99.999%
Value of interest acquired																									150,000,000	1,928,600,000
Loan repaid												16,500,000								150,000,000
Loan granted													56,600,000										37,600,000	146,400,000
Number of loans guaranteed by subsidiaries																																			2
Original loan balance																																		8,500,000
Basis of variable interest rate													6 months Libor																					Libor
Spread on variable interest rate (as a percent)													3.00%																					0.15%
Remaining balance at March 31, 2013													23,400,000						173,400,000															600,000
Interest earned													400,000	500,000					2,700,000
Sales and other revenues from related parties	$ 36,608,000	$ 10,972,000					$ 36,600,000	$ 11,000,000								$ 200,000	$ 100,000		$ 100,000																				$ 100,000		$ 100,000	$ 700,000
Number of subsidiaries involved in Mexican operations																																													3