Schedule Of Consolidated Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Plan [Member]
Components of net periodic benefit costs:
Service cost	$ 7,203	$ 6,527
Interest cost	2,802	3,000
Expected return on plan assets	(2,886)	(2,374)
Amortization of prior service credit	(45)	(45)
Amortization of actuarial loss	1,412	1,277
Settlement cost	969	0
Settlement gain on disposition of assets	(1,342)	0
Net periodic benefit cost	8,113	8,385
Other Postretirement Benefits Plan [Member]
Components of net periodic benefit costs:
Service cost	62	54
Interest cost	112	119
Expected return on plan assets	0	0
Amortization of prior service credit	0	0
Amortization of actuarial loss	119	71
Settlement cost	0	0
Settlement gain on disposition of assets	0	0
Net periodic benefit cost	$ 293	$ 244