Employee benefit plans (Tables)

6 Months Ended

Jun. 30, 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 June 30,	2016			2015			2016			2015
	(In thousands)
Components of net periodic benefit cost:
Service cost	$	—		$	46		$	374		$	425
Interest cost	4,220			4,206			895			889
Expected return on assets	(5,182		)	(5,753		)	(1,118		)	(1,223		)
Amortization of prior service cost (credit)	—			18			(343		)	(343		)
Amortization of net actuarial loss	1,514			1,813			299			553
Curtailment loss	—			258			—			—
Net periodic benefit cost, including amount capitalized	552			588			107			301
Less amount capitalized	121			53			4			33
Net periodic benefit cost	$	431		$	535		$	103		$	268

	Pension Benefits						Other Postretirement Benefits
Six Months Ended June 30,	2016			2015			2016			2015
	(In thousands)
Components of net periodic benefit cost:
Service cost	$	—		$	86		$	824		$	908
Interest cost	8,610			8,570			1,844			1,803
Expected return on assets	(10,462		)	(11,126		)	(2,267		)	(2,398		)
Amortization of prior service cost (credit)	—			36			(686		)	(685		)
Amortization of net actuarial loss	3,107			3,548			747			1,014
Curtailment loss	—			258			—			—
Net periodic benefit cost, including amount capitalized	1,255			1,372			462			642
Less amount capitalized	202			129			38			62
Net periodic benefit cost	$	1,053		$	1,243		$	424		$	580