Employee benefit plans (Tables)

3 Months Ended

Mar. 31, 2013

Defined Benefit Pension Plans [Member]

Schedule of Components of Net Periodic Credit

The components of our net periodic defined benefit pension credit for the first quarter of 2012 and 2013 are presented in the table below.

	Three months ended March 31,
	2012			2013
	(In thousands)
Service cost	$	1,168		$	1,292
Interest cost		4,385			4,022
Expected return on plan assets		(12,202	)		(13,451	)
Amortization of accumulated other comprehensive income:
Prior service cost		308			308
Actuarial losses		4,442			4,133
Total pension credit	$	(1,899	)	$	(3,696	)

OPEB [Member]

Schedule of Components of Net Periodic Credit

The components of our net periodic credit related to OPEB for the first quarter of 2012 and 2013 are presented in the table below.

	Three months ended March 31,
	2012			2013
	(In thousands)
Service cost	$	40		$	46
Interest cost		507			459
Amortization of accumulated other comprehensive income:
Prior service credit		(4,043	)		(4,043	)
Actuarial losses		1,919			1,864
Total OPEB credit	$	(1,577	)	$	(1,674	)