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Energy and Related Sales, Net - Summary of Energy and Related Sales Net (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Energy And Related Sales Net [Abstract] |  |  |
Energy sales | $ 8,189 | $ 5,284 | $ 10,992
Costs to produce | (6,784) | (4,187) | (9,319)
Net energy sales | 1,405 | 1,097 | 1,673
Renewable energy credits | 1,748 | 5,903 | 7,671
Total energy and related sales, net | $ 3,153 | $ 7,000 | $ 9,344

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- Definition Revenue from sales of excess internally generated power, net of costs to produce, and revenue from sales of renewable energy credits. + References No definition available. + Details
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