Employee benefit plans (Tables)

6 Months Ended

Jun. 30, 2018

Employee benefit plans

Schedule of net periodic benefit cost

The net periodic benefit cost was as follows (in thousands):

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018		2017		2018		2017
Service cost	$	1,032	$	680	$	2,111	$	1,296
Interest cost		68		52		139		98
Expected return on plan assets		(47)		(38)		(97)		(73)
Amortization of prior service cost		45		13		90		25
Amortization of actuarial losses		66		34		132		68
Net periodic benefit cost	$	1,164	$	741	$	2,375	$	1,414