Retirement Plans - Weighted Average Asset Allocations for Plan (Details) - Pension Plans, Defined Benefit [Member]	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocations	100.00%	100.00%
U.S. Equities securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocations	53.00%	50.00%
U.S. Debt securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocations	47.00%	50.00%