Employee benefit plans (Tables)

6 Months Ended

Jun. 30, 2015

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:

							Other
							Postretirement
	Pension Benefits						Benefits
Three Months Ended June 30,	2015			2014			2015			2014
	(In thousands)
Components of net periodic benefit cost (credit):
Service cost	$	46		$	31		$	425		$	380
Interest cost	4,206			4,405			889			924
Expected return on assets	(5,753		)	(5,484		)	(1,223		)	(1,242		)
Amortization of prior service cost (credit)	18			18			(343		)	(348		)
Amortization of net actuarial loss	1,813			1,121			553			6
Curtailment loss	258			—			—			—
Net periodic benefit cost (credit), including amount capitalized	588			91			301			(280		)
Less amount capitalized	53			73			33			(19		)
Net periodic benefit cost (credit)	$	535		$	18		$	268		$	(261	)

							Other
							Postretirement
	Pension Benefits						Benefits
Six Months Ended June 30,	2015			2014			2015			2014
	(In thousands)
Components of net periodic benefit cost (credit):
Service cost	$	86		$	64		$	908		$	759
Interest cost	8,570			8,845			1,803			1,782
Expected return on assets	(11,126		)	(10,609		)	(2,398		)	(2,309		)
Amortization of prior service cost (credit)	36			36			(685		)	(696		)
Amortization of net actuarial loss	3,548			2,434			1,014			324
Curtailment loss	258			—			—			—
Net periodic benefit cost (credit), including amount capitalized	1,372			770			642			(140		)
Less amount capitalized	129			168			62			10
Net periodic benefit cost (credit)	$	1,243		$	602		$	580		$	(150	)