Employee Pension Plans (Summary of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Summary of net periodic benefit cost
Interest cost	$ 758	$ 948
Expected return on plan assets	(1,006)	(1,043)
Amortization of net loss	592	463
Other	231	225
Net periodic benefit cost	$ 575	$ 593