Employee Benefit Plans (Summary of Net Periodic Benefit Cost) (Details) - Employee Pension Plans [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of net periodic benefit cost
Interest cost	$ 3,801	$ 3,496	$ 3,919
Service cost	900	875	850
Expected return on plan assets	(4,170)	(4,302)	(4,358)
Recognized net actuarial losses	1,933	2,067	1,897
Net periodic benefit cost	$ 2,464	$ 2,136	$ 2,308
Actuarial Assumptions Used to Determine Net Cost
Discount rate (as a percent)	4.12%	3.45%	3.90%
Expected return on assets (as a percent)	5.75%	6.00%	6.00%