Benefit Plan Schedule of components of net periodic benefit cost and other amounts recognized in OCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan, Service Cost	$ (8,319)	$ (5,873)	$ (6,547)
Defined Benefit Plan, Interest Cost	(5,283)	(5,491)	(5,236)
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	14,410	12,105	13,417
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit	(1,175)	(1,882)	(1,361)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	367	1,141	(273)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), before Tax	(10,981)	1,913	(5,122)
Defined Benefit Plan, Amortization of Gain (Loss)	1,175	1,882	1,361
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax	(9,806)	3,795	(3,761)
Total Recognized In Net Benefit Cost And Other Comprehensive Loss Income	$ (10,173)	$ 2,654	$ (3,488)