Retirement Plans - Pension Plan Asset Allocation (Details 7)	Dec. 31, 2019	Dec. 31, 2018
Retirement Plans
Target allocations	100.00%
Percentage of plan assets	100.00%	100.00%
Equity Securities
Retirement Plans
Target allocations	13.00%
Percentage of plan assets	13.00%	12.00%
Debt securities
Retirement Plans
Target allocations	83.00%
Percentage of plan assets	83.00%	84.00%
Other
Retirement Plans
Target allocations	4.00%
Percentage of plan assets	4.00%	4.00%