Employee benefit plans (Tables)

6 Months Ended

Jun. 30, 2014

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Schedule of Defined Benefit Plans Disclosures

The components of expense for the plans were as follows (in thousands):

Pension benefits:
	Three months ended June 30,						Six months ended June 30,
Components of expense	2014			2013			2014			2013
Service costs	$	289		$	241		$	565		$	481
Interest costs	754			687			1,507			1,373
Expected return on plan assets	(768		)	(659		)	(1,534		)	(1,317		)
Recognized net actuarial loss	162			344			326			688
Net periodic pension cost	$	437		$	613		$	864		$	1,225
Postretirement health care and life insurance plans:
	Three months ended June 30,						Six months ended June 30,
Components of expense	2014			2013			2014			2013
Interest costs	$	20		$	19		$	40		$	39
Amortization of prior service cost	(454		)	(454		)	(908		)	(908		)
Recognized net actuarial loss	450			456			900			912
Net periodic cost	$	16		$	21		$	32		$	43