Overview - Additional Information (Detail)	12 Months Ended
Dec. 31, 2016 segment	Dec. 31, 2016 Segment	Mar. 01, 2016	Feb. 29, 2016	Jul. 31, 2015	Jul. 30, 2015	May 29, 2015	May 28, 2015
Operating segments	3
Number of businsess segment	5	2
Laramie Energy Company
Ownership of Laramie Energy, LLC	42.30%	42.30%	42.30%	32.40%	32.40%	34.00%	34.00%	33.34%

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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