Benefit Plan (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension plan contributions			$ 0	$ 0
Service cost	$ 2,479	$ 2,080	4,958	4,160
Interest cost	1,340	1,320	2,680	2,640
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	441	92	882	184
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2,479	2,080	4,958	4,160
Interest cost	1,340	1,320	2,680	2,640
Expected return on plan assets	(3,933)	(3,602)	(7,866)	(7,204)
Recognized net actuarial loss	555	294	1,110	588
Benefit expense	441	92	882	184
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	204	219	408	583
Interest cost	149	133	298	267
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	353	352	706	850
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	204	219	408	583
Interest cost	149	133	298	267
Benefit expense	$ 353	$ 352	$ 706	$ 850