Employee Benefit Plans Table (Details) - Scenario, Forecast	12 Months Ended
	Dec. 31, 2017 USD ($)
Post-Retirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 753,000
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	3,336,000
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 0