Schedule Of Consolidated Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Plan [Member]
Components of net periodic benefit costs:
Service cost	$ 15,700	$ 5,018
Interest cost	6,443	2,350
Expected return on plan assets	(2,978)	(2,487)
Amortization of prior service credit	(45)	(45)
Amortization of actuarial loss	4,954	1,028
Settlement cost	0	1,365
Net periodic benefit cost	24,074	7,229
Other Postretirement Benefits Plan [Member]
Components of net periodic benefit costs:
Service cost	65	65
Interest cost	106	122
Expected return on plan assets	0	0
Amortization of prior service credit	0	0
Amortization of actuarial loss	160	200
Settlement cost	0	0
Net periodic benefit cost	$ 331	$ 387