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Stock Options and Warrants - Additional Information (Detail) (USD $)
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12 Months Ended | 12 Months Ended | 12 Months Ended | 12 Months Ended | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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May 31, 2013
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May 31, 2012
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May 31, 2013
Minimum
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May 31, 2012
Minimum
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May 31, 2013
Maximum
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May 31, 2012
Maximum
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May 31, 2013
Investor
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May 31, 2013
Investor
Minimum
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May 31, 2013
Investor
Maximum
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May 31, 2013
2012 Equity Incentive Plan
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May 31, 2012
2012 Equity Incentive Plan
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May 31, 2013
2012 Equity Incentive Plan
Warrant
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May 31, 2012
2012 Equity Incentive Plan
Warrant
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May 31, 2013
2012 Equity Incentive Plan
Warrant
Consultant
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May 31, 2013
2012 Equity Incentive Plan
Warrant
Consultant
Minimum
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May 31, 2013
2012 Equity Incentive Plan
Warrant
Consultant
Maximum
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
Director
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
Director
Minimum
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
Director
Maximum
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
Employees
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
Employees
October 2013
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Oct. 31, 2013
2012 Equity Incentive Plan
Stock Options
Employees
October 2013
Options Expected To Vest
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
Employees
Minimum
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May 31, 2013
2012 Equity Incentive Plan
Stock Options
Employees
Maximum
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May 31, 2013
2012 Equity Incentive Plan
Stock Options 2
Director
Maximum
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May 31, 2013
2012 Equity Incentive Plan
Stock Options 2
Employees
Minimum
October 2013
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May 31, 2013
2012 Equity Incentive Plan
Stock Options 2
Employees
Maximum
October 2013
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||||||||||||||||||||||||||
| Authorized shares that can be purchased for options and warrants issued | 7,600,000 | |||||||||||||||||||||||||||
| Shares available for future issuance | 3,000,000 | |||||||||||||||||||||||||||
| Shares available for future stock option grants | 1,976,710 | |||||||||||||||||||||||||||
| Stock options granted, shares | 11,166,274 | 3,456,088 | 148,290 | 1,225,000 | ||||||||||||||||||||||||
| Stock options granted, exercise price | $ 1.61 | $ 2.04 | $ 1.40 | $ 1.55 | $ 0.80 | $ 1.80 | ||||||||||||||||||||||
| Expiration date of stock option | 3 years | 1 year | ||||||||||||||||||||||||||
| Expiration date of stock option | 1 year | 1 year | 4 years | 4 years | 5 years | 3 years | 5 years | |||||||||||||||||||||
| Grant date fair value of options | $ 0.89 | $ 0.60 | ||||||||||||||||||||||||||
| Options vesting date | 2013-10 | |||||||||||||||||||||||||||
| Number of options expected to vest | 112,500 | 112,500 | ||||||||||||||||||||||||||
| Shares against which warrants granted to consultants | 750,000 | 515,000 | ||||||||||||||||||||||||||
| Warrants granted, exercise price | 0.75 | 2.00 | 1.00 | 5.00 | ||||||||||||||||||||||||
| Warrants latest vesting date | Apr. 30, 2013 | |||||||||||||||||||||||||||
| Warrants expiration dates | 2014-09 | 2015-10 | ||||||||||||||||||||||||||
| Fair value of warrants | $ 0.72 | $ 0.56 | ||||||||||||||||||||||||||
| Exercise price | $ 0.25 | |||||||||||||||||||||||||||
| Compensation expense associated with warrants | $ 1,128,000 | $ 3,262,000 | $ 1,692,000 | $ 540,000 | ||||||||||||||||||||||||
| Warrants to purchase common shares, shares | 8,527,984 | |||||||||||||||||||||||||||
| Net cash proceeds from exercise of common stock warrants | 201,000 | |||||||||||||||||||||||||||
| Grant date fair value of options and warrants vested | 8,889,000 | 1,562,000 | ||||||||||||||||||||||||||
| Unrecognized compensation costs | $ 1,748,000 | |||||||||||||||||||||||||||
| Weighted average period over which unrecognized compensation costs is expected to be recognized | 1 year 6 months 26 days | |||||||||||||||||||||||||||