Employee benefit plans (Tables)

3 Months Ended

Mar. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Schedule of net benefit costs

Components of net periodic benefit cost for the Company's pension and other postretirement benefit plans were as follows:

	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2016			2015			2016			2015
	(In thousands)
Components of net periodic benefit cost:
Service cost	$	—		$	40		$	450		$	483
Interest cost	4,390			4,364			949			914
Expected return on assets	(5,280		)	(5,373		)	(1,149		)	(1,175		)
Amortization of prior service cost (credit)	—			18			(343		)	(342		)
Amortization of net actuarial loss	1,593			1,735			448			461
Net periodic benefit cost, including amount capitalized	703			784			355			341
Less amount capitalized	81			76			34			29
Net periodic benefit cost	$	622		$	708		$	321		$	312