Employee Benefit Plans - Summary of Participants (Details)	Jan. 01, 2019 employee
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Active Employees	3,521
Retirees and Beneficiaries	12,016
Other	4,012
Total	19,549
Post-retirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Active Employees	616
Retirees and Beneficiaries	8,393
Other	40
Total	9,049