Employee benefit plans (Tables)

9 Months Ended

Sep. 30, 2018

Retirement Benefits [Abstract]

Schedule of net benefit costs

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

	Pension Benefits						Other Postretirement Benefits
Three Months Ended September 30,	2018			2017			2018			2017
	(In thousands)
Components of net periodic benefit cost (credit):
Service cost	$	—		$	—		$	374		$	377
Interest cost	3,648			4,052			725			816
Expected return on assets	(5,188		)	(5,132		)	(1,217		)	(1,160		)
Amortization of prior service credit	—			—			(349		)	(343		)
Amortization of net actuarial loss	1,751			1,589			160			213
Net periodic benefit cost (credit), including amount capitalized	211			509			(307		)	(97		)
Less amount capitalized	—			65			46			(95		)
Net periodic benefit cost (credit)	$	211		$	444		$	(353	)	$	(2	)

	Pension Benefits						Other Postretirement Benefits
Nine Months Ended September 30,	2018			2017			2018			2017
	(In thousands)
Components of net periodic benefit cost (credit):
Service cost	$	—		$	—		$	1,121		$	1,130
Interest cost	10,943			12,155			2,175			2,449
Expected return on assets	(15,565		)	(15,395		)	(3,650		)	(3,480		)
Amortization of prior service credit	—			—			(1,046		)	(1,029		)
Amortization of net actuarial loss	5,254			4,767			480			649
Net periodic benefit cost (credit), including amount capitalized	632			1,527			(920		)	(281		)
Less amount capitalized	—			245			128			(248		)
Net periodic benefit cost (credit)	$	632		$	1,282		$	(1,048	)	$	(33	)