Benefit Plan (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,468	$ 1,637	$ 4,404	$ 4,911
Interest cost	1,373	1,309	4,119	3,927
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	285	(68)	855	(204)
Pension plan contributions			0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1,468	1,637	4,404	4,911
Interest cost	1,373	1,309	4,119	3,927
Expected return on plan assets	(3,026)	(3,354)	(9,078)	(10,062)
Recognized net actuarial loss	470	340	1,410	1,020
Benefit expense	285	(68)	855	(204)
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	202	157	604	635
Interest cost	165	188	495	349
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	367	345	1,099	984
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	202	157	604	635
Interest cost	165	188	495	349
Benefit expense	$ 367	$ 345	$ 1,099	$ 984