Employee benefit plans (Tables)

9 Months Ended

Sep. 30, 2018

Employee benefit plans

Schedule of net periodic benefit cost

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

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Service cost	$	1,041	$	760	$	3,152	$	2,056
Interest cost		69		57		208		155
Expected return on plan assets		(48)		(43)		(145)		(116)
Amortization of prior service cost		45		12		135		37
Amortization of actuarial losses		66		34		198		102
Net periodic benefit cost	$	1,173	$	820	$	3,548	$	2,234