Employee benefit plans (Tables)

6 Months Ended

Jun. 30, 2017

Employee benefit plans

Schedule of components of net periodic benefit cost

	Pension Benefits
Three Months Ended June 30,	2017		2016
Components of net periodic pension cost:
Interest cost	$	217	$	166
Expected return on plan assets		(305)		(223)
Amortization of unrecognized net gain		65		52
Net periodic other benefit cost	$	(23)	$	(5)
	Pension Benefits
Six Months Ended June 30,	2017		2016
Components of net periodic pension cost:
Interest cost	$	217	$	333
Expected return on plan assets		(305)		(447)
Amortization of unrecognized net gain		65		104
Net periodic other benefit cost	$	(23)	$	(10)