Benefit Plan (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension plan contributions			$ 0	$ 0
Service cost	$ 2,479	$ 2,080	7,437	6,240
Interest cost	1,340	1,320	4,020	3,960
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	441	92	1,323	276
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2,479	2,080	7,437	6,240
Interest cost	1,340	1,320	4,020	3,960
Expected return on plan assets	(3,933)	(3,602)	(11,799)	(10,806)
Recognized net actuarial loss	555	294	1,665	882
Benefit expense	441	92	1,323	276
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	203	218	611	801
Interest cost	150	134	448	401
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	353	352	1,059	1,202
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	203	218	611	801
Interest cost	150	134	448	401
Benefit expense	$ 353	$ 352	$ 1,059	$ 1,202