Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of the net periodic pension cost:
Interest cost	$ 736	$ 971	$ 939
Expected return on plan assets	(1,340)	(1,671)	(1,717)
Amortization of actuarial losses	686	957	826
Amortization of prior service cost	29	29
Net periodic pension cost	$ 111	$ 286	$ 48