Basis of Presentation and Principles of Consolidation - Concentration of Credit Risks (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Concentration Risk [Line Items]
Excess tax benefits	$ 0	$ 0	$ 1,500,000	$ 0
Sales | Customer Concentration Risk | Murphy USA
Concentration Risk [Line Items]
Major customer percentage of net sales	12.80%		12.90%
Sales | Customer Concentration Risk | Alimentation Couche-Tard, Inc and Murphy USA
Concentration Risk [Line Items]
Major customer percentage of net sales		24.60%		23.30%
Accounting Standards Update 2016-09
Concentration Risk [Line Items]
Excess tax benefits			$ 1,500,000
Accounting Standards Update 2015-17
Concentration Risk [Line Items]
Current deferred income tax assets					$ (4,700,000)
Current deferred income tax liabilities					(100,000)
Non-current deferred income tax liabilities					4,700,000
Net non-current deferred income tax assets					$ 100,000