Benefit Plan (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension plan contributions			$ 0	$ 0
Service cost	$ 2,080	$ 1,468	4,160	2,936
Interest cost	1,320	1,373	2,640	2,746
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	91	285	182	570
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2,080	1,468	4,160	2,936
Interest cost	1,320	1,373	2,640	2,746
Expected return on plan assets	(3,603)	(3,026)	(7,206)	(6,052)
Recognized net actuarial loss	294	470	588	940
Benefit expense	91	285	182	570
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	219	201	583	402
Interest cost	133	165	267	330
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	352	366	850	732
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	219	201	583	402
Interest cost	133	165	267	330
Benefit expense	$ 352	$ 366	$ 850	$ 732