Employee Benefits - Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Amounts Recognized in Accumulated Other Comprehensive Income (Loss), Net of Tax
Net Actuarial Gains (Losses)	$ (43,101)	$ (41,404)
Net Prior Service Credit	0	0
Total Amounts Recognized in Accumulated Other Comprehensive Income (Loss), Net of Tax	(43,101)	(41,404)
Postretirement Benefits
Amounts Recognized in Accumulated Other Comprehensive Income (Loss), Net of Tax
Net Actuarial Gains (Losses)	(1,613)	1,003
Net Prior Service Credit	1,464	1,645
Total Amounts Recognized in Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (149)	$ 2,648