Organization, Use of Estimates and Basis of Presentation (Details) (USD $)	3 Months Ended	6 Months Ended
Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Basic loss per share computation
Net loss attributable to common stockholders	$ (3,078,000)us-gaap_NetIncomeLoss	$ (2,318,000)us-gaap_NetIncomeLoss	$ (6,684,000)us-gaap_NetIncomeLoss	$ (4,556,000)us-gaap_NetIncomeLoss
Weighted Average common shares - basic	66,887,331	66,863,147	66,886,234	66,857,630
Basic net loss per share	$ (0.05)us-gaap_EarningsPerShareBasic	$ (0.03)us-gaap_EarningsPerShareBasic	$ (0.10)us-gaap_EarningsPerShareBasic	$ (0.07)us-gaap_EarningsPerShareBasic
Diluted loss per share computation
Net loss attributable to common stockholders	(3,078,000)us-gaap_NetIncomeLoss	(2,318,000)us-gaap_NetIncomeLoss	(6,684,000)us-gaap_NetIncomeLoss	(4,556,000)us-gaap_NetIncomeLoss
Less: Gain on derivative warrant liability	624,993	0	780,627	0
Loss available to common stockholders	$ (3,702,993)	$ (2,318,000)	$ (7,464,627)	$ (4,556,000)
Weighted Average common shares	66,887,331	66,863,147	66,886,234	66,857,630
Incremental shares from assumed exercise of warrants and stock options	967,994	0	967,994	0
Adjusted weighted average share - diluted	67,855,325	66,863,147	67,854,228	66,857,630
Diluted net loss per share	$ (0.05)us-gaap_EarningsPerShareDiluted	$ (0.03)us-gaap_EarningsPerShareDiluted	$ (0.11)us-gaap_EarningsPerShareDiluted	$ (0.07)us-gaap_EarningsPerShareDiluted

Number of shares issued upon exercise of warrants and stock options during the reporting period.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Aggregate gain on all derivative instruments recognized in earnings during the period, before tax effects.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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