Pension Benefits and Postretirement Benefits Other Than Pensions - Narrative (Details)	9 Months Ended
	Sep. 30, 2020 employees
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Number of participants and beneficiaries	8,510
Number of active employees	1,040
Postretirement Benefits Other than Pensions
Defined Benefit Plan Disclosure [Line Items]
Number of retired employees covered	590
Number of active employees covered	500