Pension and Other Postretirement Employee Benefits (Components Of Net Periodic Cost (Benefit)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,913	$ 1,862
Interest cost	3,914	4,081
Expected return on plan assets	(4,708)	(4,603)
Amortization of prior service cost (credit)	46	72
Amortization of actuarial loss	4,150	3,856
Net periodic cost (benefit)	5,315	5,268
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	44	3
Interest cost	319	321
Amortization of prior service cost (credit)	(2,219)	(2,219)
Amortization of actuarial loss	355	398
Net periodic cost (benefit)	$ (1,501)	$ (1,497)