Retirement Benefits - Schedule of Pension Plan's Asset Allocations by Asset Category (Details)	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	100.00%	100.00%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	2.00%	4.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	46.00%	44.00%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	15.00%	15.00%
Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	2.00%	2.00%
Private assets
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	11.00%	12.00%
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Pension plans weighted average asset allocation	24.00%	23.00%