Retirement Benefits (Summary Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Amortization of net (income) loss	$ 2,730	$ 1,213
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,738	4,011
Interest cost	1,999	2,483
Expected return on plan assets	(5,580)	(5,197)
Net periodic benefit cost	1,887	2,510
Post-Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	281	141
Interest cost	181	215
Amortization of prior service cost	144	48
Net periodic benefit cost	$ 318	$ 308