Pension plans and other postretirement benefits (Tables)

3 Months Ended

Mar. 31, 2017

Compensation And Retirement Disclosure [Abstract]

Net Periodic Defined Benefit Cost for Defined Benefit Plans

Net periodic defined benefit cost for defined benefit plans consisted of the following:

	Pension Benefits						Other Postretirement Benefits
	Three Months Ended March 31
	2017			2016			2017			2016
	(In thousands)
Service cost	$	4,908			6,382			383		458
Interest cost on projected benefit obligation		19,691			20,883			1,080			1,205
Expected return on plan assets		(27,200	)		(27,814	)		—			—
Amortization of prior service cost (credit)		125			(825	)		(350	)		(350	)
Amortization of net actuarial loss		6,800			8,300			(25	)		—
Net periodic benefit cost	$	4,324			6,926			1,088			1,313