Employee Benefit Plans - Summary of Participants (Details)	Jan. 01, 2017 employee
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Active Employees	3,566
Retirees and Beneficiaries	12,081
Other	4,262
Total	19,909
Post-retirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Active Employees	660
Retirees and Beneficiaries	9,030
Other	23
Total	9,713