Derivative and Hedging Financial Instruments - Summary of Realized and Unrealized Gains and Losses Related to Derivative Instrument (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Abstract]
Realized gains (loss) on derivatives	$ 949,094us-gaap_GainLossOnSaleOfDerivatives	$ (7,000,000)us-gaap_GainLossOnSaleOfDerivatives
Change in fair value of derivatives	7,639,441	682,505
Total realized and unrealized gains/(losses) recorded	8,588,535
Total realized and unrealized gains/(losses) recorded		(5,885,337)
(Decrease) in fair value of derivatives		(125,773)us-gaap_DerivativeLossOnDerivative
Increase in fair value of derivatives		$ 808,278us-gaap_DerivativeGainOnDerivative

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Amount of increase in the fair value of derivatives recognized in the income statement.

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Amount of realized and unrealized gain of derivative instruments not designated or qualifying as hedging instruments.

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Amount of realized and unrealized loss of derivative instruments not designated or qualifying as hedging instruments.

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Amount of decrease in the fair value of derivatives recognized in the income statement.

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The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

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