Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of the net periodic pension cost:
Interest cost	$ 971	$ 939	$ 991
Expected return on plan assets	(1,671)	(1,717)	(1,665)
Amortization of actuarial losses	957	826	1,045
Amortization of prior service cost	29
Net periodic pension cost	$ 286	$ 48	$ 371