Employee Benefit Plans (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Benefit Plans [Abstract]
Service cost	$ 3,140	$ 2,885	$ 2,324
Interest cost on projected benefit obligation	2,449	2,402	2,328
Expected return on plan assets	(4,775)	(4,600)	(4,820)
Amortization of unrecognized loss	1,142	938	926
Amortization of unrecognized prior service credit	17	20	20
Net periodic benefit expense	$ 1,973	$ 1,645	$ 778