Employee Benefit Plans and Other Postretirement Benefits (Components Of Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 31,584	$ 33,437	$ 40,039
Interest cost	85,076	90,827	87,345
Special early retirement benefits	0	0	10,563
Expected return on plan assets	(141,385)	(145,781)	(144,929)
Prior service cost (credit)	1,018	1,019	435
Net loss	43,993	46,351	54,709
Settlement loss	0	1,463	368
Net periodic benefit cost	20,286	27,316	48,530
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Service cost	7,500	7,478	8,259
Interest cost	13,648	14,814	14,166
Special early retirement benefits	0	0	622
Expected return on plan assets	(12,623)	(12,069)	(11,506)
Prior service cost (credit)	(2,171)	(2,803)	(3,217)
Net loss	3,261	3,537	3,971
Settlement loss	0	0	0
Net periodic benefit cost	$ 9,615	$ 10,957	$ 12,295