Debt - Mid Pac Agreement (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Apr. 01, 2015
Debt Instrument [Line Items]
Long-term debt	$ 165,212,000	$ 370,396,000
Secured Debt | Mid Pac Credit Agreement
Debt Instrument [Line Items]
Line credit maximum borrowing amount			$ 50,000,000
Revolving Credit Facility | Mid Pac Credit Agreement
Debt Instrument [Line Items]
Line credit maximum borrowing amount			5,000,000
Mid Pac Petroleum, LLC | Mid Pac Credit Agreement
Debt Instrument [Line Items]
Long-term debt			55,000,000
Mid Pac Petroleum, LLC
Debt Instrument [Line Items]
Financing costs expensed	$ 381,000
Mid Pac Petroleum, LLC | Mid Pac Petroleum, LLC
Debt Instrument [Line Items]
Long-term debt			$ 45,300,000