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Significant Concentrations - Schedule of Purchasers Accounted More than Ten Percent of Total Sales (Detail) | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
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Musket Corporation [Member] |  |  |  |  |  |
Significant Concentrations [Line Items] |  |  |  |  |  |
Percent of sales to total sales | 10.00% |  |  | [1] |  | [1]
Texon L.P. [Member] |  |  |  |  |  |
Significant Concentrations [Line Items] |  |  |  |  |  |
Percent of sales to total sales |  | [1] | 18.00% |  | 19.00% |
Plains All American Pipeline L.P. [Member] |  |  |  |  |  |
Significant Concentrations [Line Items] |  |  |  |  |  |
Percent of sales to total sales |  | [1] | 16.00% |  | 28.00% |
Enserco Energy Inc. [Member] |  |  |  |  |  |
Significant Concentrations [Line Items] |  |  |  |  |  |
Percent of sales to total sales |  | [1] | 15.00% |  |  | [1]
Whiting Petroleum Corporation [Member] |  |  |  |  |  |
Significant Concentrations [Line Items] |  |  |  |  |  |
Percent of sales to total sales |  | [1] |  | [1] | 11.00% |
[1] | Not applicable as the sales to these purchasers did not account for more than 10% of the Company's total sales for such respective periods.

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- Details
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- Definition The percentage of net product revenue to total net revenue from the sale of goods as of year end. + References No definition available. + Details
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