Schedule Of Consolidated Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Plan [Member]
Components of net periodic benefit costs:
Service cost	$ 6,269	$ 5,230	$ 21,969	$ 10,248
Interest cost	2,795	2,582	9,238	4,932
Expected return on plan assets	(3,024)	(2,646)	(6,002)	(5,133)
Amortization of prior service credit	(46)	(46)	(91)	(91)
Amortization of actuarial loss	1,569	1,783	6,523	2,811
Settlement cost	0	361	0	1,726
Net periodic benefit cost	7,563	7,264	31,637	14,493
Other Postretirement Benefits Plan [Member]
Components of net periodic benefit costs:
Service cost	51	66	116	131
Interest cost	102	123	208	245
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	0	0	0	0
Amortization of actuarial loss	134	200	294	400
Settlement cost	0	0	0	0
Net periodic benefit cost	$ 287	$ 389	$ 618	$ 776