Employee Benefit Plans and Other Postretirement Benefits - Schedule Of Net Periodic Benefit Cost Recognized In Accumulated And Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Prior service credits	$ (5,712)	$ (6,489)
Net actuarial loss	445,804	496,919
Amounts included in other comprehensive income, net of tax	440,092	490,430
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Prior service credits	(5,438)	(7,559)
Net actuarial loss	(4,942)	(1,321)
Amounts included in other comprehensive income, net of tax	$ (10,380)	$ (8,880)