Pension and Other Postretirement Employee Benefits (Components Of Net Periodic Cost (Benefit)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,178	$ 1,515	$ 4,091	$ 3,377
Interest cost	4,390	3,967	8,304	8,048
Expected return on plan assets	(5,135)	(4,601)	(9,843)	(9,204)
Amortization of prior service cost (credit)	47	72	93	144
Amortization of actuarial loss	4,144	3,386	8,294	7,242
Net periodic cost (benefit)	5,624	4,339	10,939	9,607
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	99	4	143	7
Interest cost	381	310	700	631
Amortization of prior service cost (credit)	(2,220)	(2,220)	(4,439)	(4,439)
Amortization of actuarial loss	301	371	656	769
Net periodic cost (benefit)	$ (1,439)	$ (1,535)	$ (2,940)	$ (3,032)