Summary of Significant Accounting Policies (Details) - Customer Concentration Risk - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Net sales \| Murphy USA
Concentration Risk [Line Items]
Major customer percentage of net sales	14.00%	13.00%
Accounts receivable \| GPM Southeast, LLC
Concentration Risk [Line Items]
Major customer percentage of net sales	11.00%
Concentration risk, amount	$ 43.3

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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