Employee Benefit Plans (Summary of Net Periodic Benefit Cost) (Details) - Employee Pension Plans [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of net periodic benefit cost
Interest cost	$ 3,496	$ 3,919	$ 4,153
Service cost	875	850	600
Expected return on plan assets	(4,302)	(4,358)	(4,803)
Recognized net actuarial losses	2,067	1,897	1,745
Net periodic benefit cost	$ 2,136	$ 2,308	$ 1,695
Actuarial Assumptions Used to Determine Net Cost
Discount rate (as a percent)	3.45%	3.90%	4.10%
Expected return on assets (as a percent)	6.00%	6.00%	6.00%