Pension - Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Components of net periodic benefit cost:
Service cost	$ 9	$ 9	$ 18	$ 18
Interest cost	9	10	18	20
Expected return on plan assets	(14)	(17)	(29)	(34)
Amortization of actuarial loss	22	22	44	44
Total non-service cost	17	15	33	30
Net periodic pension cost	$ 26	$ 24	$ 51	$ 48