Overview (Detail) barrel / d in Thousands	6 Months Ended
Jun. 30, 2019 barrel / d segment gasoline_store_facility refinery
Schedule of Equity Method Investments [Line Items]
Operating segments \| segment	3
Number of owned and operated refineries \| refinery	3
Oil and gas refinery capacity \| barrel / d	200
Number of retail gasoline, convenience stores, rebranded	25
Number of retail gasoline, convenience store facilities	34
Laramie Energy Company
Schedule of Equity Method Investments [Line Items]
Ownership interest in Laramie Energy, LLC	46.00%

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration