Savings Plans, Pension Plans and Other Postretirement Employee Benefits (Pre-Tax Components Of Net Periodic Cost (Benefit)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6,753	$ 6,508	$ 6,159
Interest cost	16,096	17,020	17,012
Expected return on plan assets	(18,406)	(18,999)	(20,804)
Amortization of prior service cost (credit)	288	518	605
Amortization of actuarial loss	14,484	16,339	17,937
Net periodic cost (benefit)	19,215	21,386	20,909
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	14	22
Interest cost	1,262	1,421	1,456
Amortization of prior service cost (credit)	(8,877)	(8,877)	(9,312)
Amortization of actuarial loss	1,537	1,717	2,047
Net periodic cost (benefit)	$ (6,064)	$ (5,725)	$ (5,787)