Pension plans and other postretirement benefits (Tables)

6 Months Ended

Jun. 30, 2018

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
	2018			2017			2018			2017
	(In thousands)
Service cost	$	5,069			5,189			243		202
Interest cost on projected benefit obligation		18,548			19,943			589			778
Expected return on plan assets		(30,688	)		(27,062	)		—			—
Amortization of prior service cost (credit)		153			154			(1,189	)		(329	)
Amortization of net actuarial loss (gain)		10,796			7,831			(213	)		(469	)
Net periodic benefit cost	$	3,878			6,055			(570	)		182

	Pension Benefits						Other Postretirement Benefits
	Six Months Ended June 30
	2018			2017			2018			2017
	(In thousands)
Service cost	$	10,172			10,097			469			585
Interest cost on projected benefit obligation		37,353			39,634			1,146			1,858
Expected return on plan assets		(61,563	)		(54,262	)		—			—
Amortization of prior service cost (credit)		278			279			(2,364	)		(679	)
Amortization of net actuarial loss (gain)		21,896			14,631			(413	)		(494	)
Net periodic benefit cost	$	8,136			10,379			(1,162	)		1,270