Pension Plans and Other Postretirement Benefit Plans - Investment Allocation Percentages By Asset Classes (Details)	Dec. 31, 2020	Dec. 31, 2019
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	35.00%	35.00%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	49.00%	49.00%
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	7.00%	7.00%
Absolute Return [Member]
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	9.00%	9.00%