Pension and Other Postretirement Employee Benefits (Components Of Net Periodic Cost (Benefit)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,045	$ 2,290
Interest cost	2,633	3,564
Expected return on plan assets	(3,525)	(4,586)
Amortization of prior service cost (credit)	21	28
Amortization of actuarial loss	3,721	4,154
Net periodic cost before pension settlement charge	4,895	5,450
Pension settlement charge		42,988
Net periodic cost	4,895	48,438
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	168	143
Interest cost	317	375
Amortization of prior service cost (credit)	(298)	(319)
Amortization of actuarial loss	545	419
Net periodic cost before pension settlement charge	732	618
Net periodic cost	$ 732	$ 618