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Significant Concentrations - Additional Information (Detail) - Sales	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017
Phillips 66 Company
Concentration Risk [Line Items]
Concentration risk (percent)	14.00%
Shell Trading (US) Company
Concentration Risk [Line Items]
Concentration risk (percent)		16.00%

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

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.

+ References

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