Schedule Of Consolidated Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plan [Member]
Components of net periodic benefit costs:
Service cost	$ 5,230	$ 4,405	$ 10,248	$ 9,093
Interest cost	2,582	1,933	4,932	3,978
Expected return on plan assets	(2,646)	(2,331)	(5,133)	(4,459)
Amortization of prior service credit	(46)	(45)	(91)	(90)
Amortization of actuarial loss	1,783	1,107	2,811	2,324
Settlement cost	361	0	1,726	0
Net periodic benefit cost (credit)	7,264	5,069	14,493	10,846
Other Postretirement Benefit Plan [Member]
Components of net periodic benefit costs:
Service cost	66	62	131	123
Interest cost	123	110	245	220
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	0	(929)	0	(1,857)
Amortization of actuarial loss	200	185	400	369
Settlement cost	0	0	0	0
Net periodic benefit cost (credit)	$ 389	$ (572)	$ 776	$ (1,145)