Employee Benefit Plans (Changes In Benefit Obligations And Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	$ 225,970	$ 209,591
Service cost	20,497	18,179	$ 18,890
Interest cost	9,865	7,950	7,754
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	0	0
Actuarial loss	59,686	1,050
Benefits paid	(11,484)	(10,053)
Settlements	(6,678)	(747)
Benefit obligation at end of year	297,856	225,970	209,591
Change in plan assets:
Beginning balance	166,906	142,742
Employer contributions	26,533	25,972
Plan participants’ contributions	0	0
Actual return on plan assets	23,409	8,992
Defined Benefit Plan, Plan Assets, Benefits Paid	11,484	10,053
Defined Benefit Plan, Plan Assets, Payment for Settlement	(6,678)	(747)
Fair value of plan assets at end of year	198,686	166,906	142,742
Funded status at end of year	(99,170)	(59,064)
Accumulated benefit obligation	206,480	160,642
Other Postretirement Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	13,011	11,314
Service cost	243	235	243
Interest cost	475	489	438
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	280	217
Actuarial loss	(535)	1,481
Benefits paid	(714)	(725)
Settlements	0	0
Benefit obligation at end of year	12,760	13,011	11,314
Change in plan assets:
Beginning balance	0	0
Employer contributions	434	508
Plan participants’ contributions	280	217
Actual return on plan assets	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	714	725
Defined Benefit Plan, Plan Assets, Payment for Settlement	0	0
Fair value of plan assets at end of year	0	0	$ 0
Funded status at end of year	$ (12,760)	$ (13,011)