Benefit Plan (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension plan contributions	$ 0	$ 0
Service cost	2,080	1,468
Interest cost	1,320	1,373
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	91	285
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2,080	1,468
Interest cost	1,320	1,373
Expected return on plan assets	(3,603)	(3,026)
Recognized net actuarial loss	294	470
Benefit expense	91	285
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	364	201
Interest cost	134	165
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	498	366
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	364	201
Interest cost	134	165
Benefit expense	$ 498	$ 366