Employee Benefit Plans - Summary of Participants (Details)	Jan. 01, 2017 employee
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Active Employees	3,744
Retirees and Beneficiaries	12,723
Other	3,591
Total	20,058
Post-retirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Active Employees	458
Retirees and Beneficiaries	9,940
Other	36
Total	10,434