Pension Benefits - Actuarial Assumptions Pension Expense (Details) - Pension Plans, Defined Benefit	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Weighted-average Discount Rate	4.28%	3.63%	4.19%
Service Cost Discount Rate	4.26%	3.61%	4.15%
Interest Cost Discount Rate	3.91%	3.26%	3.52%
Rate of Increase in Future Compensation Levels	3.40%	3.40%	2.56%
Expected Long Term Rate of Return on Plan Assets	5.70%	5.35%	5.80%