Benefit Plan (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,468	$ 1,637	$ 2,936	$ 3,274
Interest cost	1,373	1,309	2,746	2,618
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	285	(68)	570	(136)
Pension plan contributions			0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1,468	1,637	2,936	3,274
Interest cost	1,373	1,309	2,746	2,618
Expected return on plan assets	(3,026)	(3,354)	(6,052)	(6,708)
Recognized net actuarial loss	470	340	940	680
Benefit expense	285	(68)	570	(136)
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	201	244	402	478
Interest cost	165	44	330	161
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	366	288	732	639
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	201	244	402	478
Interest cost	165	44	330	161
Benefit expense	$ 366	$ 288	$ 732	$ 639