Employee Retirement Benefits - Assumptions Used for Periodic Income (Details) - Pension Benefits [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.22%	4.26%	3.59%
Salary increase	4.40%	4.40%	4.10%
Expected long-term rate of return, net of management fees	7.35%	7.35%	7.35%