Retirement Plans - Summary of Pension Plan Asset Allocation (Details)	Dec. 31, 2020	Dec. 31, 2019
Retirement Plans
Target Allocations	100.00%
Percentage of plan assets	100.00%	100.00%
Equity Securities
Retirement Plans
Target Allocations	0.00%
Percentage of plan assets	13.00%	13.00%
Fixed income/Debt securities
Retirement Plans
Target Allocations	100.00%
Percentage of plan assets	83.00%	83.00%
Other
Retirement Plans
Target Allocations	0.00%
Percentage of plan assets	4.00%	4.00%