RELATED PARTY TRANSACTIONS: (Tables)

12 Months Ended

Dec. 31, 2017

RELATED PARTY TRANSACTIONS:

Schedule of receivable and payable balances with related parties

        Receivable and payable balances with related parties are shown below (in millions):

	At December 31,
	2017		2016
Related parties receivable current:
Grupo Mexico and affiliates:
Mexico Generadora de Energia S. de R.L. ("MGE")	$	16.2	$	10.2
Asarco LLC		4.1		5.5
Grupo Mexico		2.8		4.5
Compañia Perforadora Mexico S.A.P.I. de C.V. and affiliates		1.4		1.3
Mexico Proyectos y Desarrollos, S.A. de C.V. and affiliates		1.1		1.5
Operadora de Generadoras de Energia Mexico S.A. de C.V.		—		0.1
Related to the controlling group:
Operadora de Cinemas S.A. de C.V.		0.3		0.2
Boutique Bowling de Mexico S.A. de C.V.		0.2		0.1
	$	26.1	$	23.4
Related parties payable:
Grupo Mexico and affiliates:
MGE	$	38.5	$	13.9
Asarco LLC		24.2		36.3
Mexico Proyectos y Desarrollos S.A. de C.V. and affiliates		21.7		7.8
Ferrocarril Mexicano S.A. de C.V.		2.6		3.0
Eolica El Retiro, S.A.P.I. de C.V.		0.8		0.1
Grupo Mexico		0.7		0.1
Related to the controlling group:
Operadora de Cinemas S.A. de C.V.		0.7		0.4
Boutique Bowling de Mexico S.A. de C.V.		0.6		0.2
Mexico Transportes Aereos S.A. de C.V. ("Mextransport")		0.3		0.1
Related to SCC executive officers:
Breaker, S.A. de C.V. and affiliates ("Breaker")		—		0.3
	$	90.1	$	62.2

Grupo Mexico and affiliates

RELATED PARTY TRANSACTIONS:

Schedule of purchase and sales activities with related parties

        The following table summarize the purchase and sale activities with Grupo Mexico and its affiliates in 2017, 2016 and 2015 (in millions):

	2017		2016		2015
Purchase activity
Asarco LLC	$	37.2	$	30.3	$	32.0
Compañia Perforadora Mexico S.A.P.I. de C.V. and affiliates		—		0.3		0.3
Eolica El Retiro, S.A.P.I. de C.V.		3.3		2.0		6.6
Ferrocarril Mexicano, S.A. de C.V.		43.5		42.7		27.3
Grupo Mexico		14.0		13.8		13.8
Mexico Proyectos y Desarrollos S.A. de C.V. and affiliates		152.9		76.0		57.3
MGE		223.7		233.8		143.3
Total purchases	$	474.6	$	398.9	$	280.6
Sales activity
Asarco LLC	$	96.2	$	37.1	$	72.3
Compañia Perforadora Mexico S.A.P.I. de C.V. and affiliates		0.2		0.6		0.6
Grupo Mexico		0.2		0.6		0.5
Mexico Proyectos y Desarrollos S.A. de C.V. and affiliates		—		0.4		0.8
Operadora de Generadoras de Energia Mexico S.A. de C.V		—		0.1		—
MGE		101.0		95.9		81.7
Total sales	$	197.6	$	134.7	$	155.9

Related to the controlling group

RELATED PARTY TRANSACTIONS:

Schedule of purchase and sales activities with related parties

        The following table summarizes the purchase and sales activities with other Larrea family companies in 2017, 2016 and 2015 (in millions):

	2017		2016		2015
Purchase activity
Boutique Bowling de Mexico S.A. de C.V.	$	0.3	$	0.4	$	0.4
Mextransport		1.3		2.0		2.0
Operadora de Cinemas S.A. de C.V.		0.1		0.5		0.5
Total purchases	$	1.7	$	2.9	$	2.9
Sales activity
Boutique Bowling de Mexico S.A. de C.V.	$	0.2	$	0.2	$	0.3
Mextransport		0.3		0.2		0.3
Operadora de Cinemas S.A. de C.V.		0.2		0.1		0.2
Total sales	$	0.7	$	0.5	$	0.8

Related to SCC executive officers

RELATED PARTY TRANSACTIONS:

Schedule of purchase activity with related parties

        The following table summarizes the purchase activities with companies with relationships to SCC executive officers in 2017, 2016 and 2015 (in millions):

	2017		2016		2015
Breaker	$	—	$	0.5	$	5.5
Higher Technology S.A.C.		—		1.0		1.4
Servicios y Fabricaciones Mecanicas S.A.C.		0.2		0.5		0.7
Sempertrans		—		—		1.2
Total purchased	$	0.2	$	2.0	$	8.8