Benefit Plan (Components Of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,468	$ 1,637
Interest cost	1,373	1,309
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	285	(68)
Pension plan contributions	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1,468	1,637
Interest cost	1,373	1,309
Expected return on plan assets	(3,026)	(3,354)
Recognized net actuarial loss	470	340
Benefit expense	285	(68)
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	201	233
Interest cost	165	117
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	366	350
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	201	233
Interest cost	165	117
Benefit expense	$ 366	$ 350