Pension plans and other postretirement benefits (Tables)

6 Months Ended

Jun. 30, 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 June 30
	2017			2016			2017			2016
	(In thousands)
Service cost	$	5,189			6,137			202		340
Interest cost on projected benefit obligation		19,943			20,822			778			1,281
Expected return on plan assets		(27,062	)		(26,423	)		—			—
Amortization of prior service cost (credit)		154			(789	)		(329	)		(330	)
Amortization of net actuarial loss (gain)		7,831			6,773			(469	)		30
Net periodic benefit cost	$	6,055			6,520			182			1,321

	Pension Benefits						Other Postretirement Benefits
	Six Months Ended June 30
	2017			2016			2017			2016
	(In thousands)
Service cost	$	10,097			12,519			585			798
Interest cost on projected benefit obligation		39,634			41,705			1,858			2,486
Expected return on plan assets		(54,262	)		(54,237	)		—			—
Amortization of prior service cost (credit)		279			(1,614	)		(679	)		(680	)
Amortization of net actuarial loss (gain)		14,631			15,073			(494	)		30
Net periodic benefit cost	$	10,379			13,446			1,270			2,634