Schedule Of Consolidated Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Plan [Member]
Components of net periodic benefit costs:
Service cost	$ 6,898	$ 6,260	$ 20,836	$ 19,145
Interest cost	2,738	3,026	8,251	9,136
Expected return on plan assets	(2,829)	(2,354)	(8,524)	(7,045)
Amortization of prior service credit	(46)	(46)	(136)	(136)
Amortization of actuarial loss	1,346	1,352	4,080	4,137
Settlement cost	0	439	969	2,499
Settlement gain on disposition of assets			(1,342)	0
Net periodic benefit cost	8,107	8,677	24,134	27,736
Other Postretirement Benefits Plan [Member]
Components of net periodic benefit costs:
Service cost	64	48	193	145
Interest cost	121	126	360	380
Expected return on plan assets	0	0	0	0
Amortization of prior service credit	0	0	0	0
Amortization of actuarial loss	127	60	382	248
Settlement cost	0	0	0	0
Settlement gain on disposition of assets			0	0
Net periodic benefit cost	$ 312	$ 234	$ 935	$ 773