Quarterly report pursuant to Section 13 or 15(d)

Assumptions used in Estimating Fair Value of Warrant Derivative Liability (Detail)

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Assumptions used in Estimating Fair Value of Warrant Derivative Liability (Detail) - $ / shares
6 Months Ended 12 Months Ended
Sep. 15, 2016
Nov. 30, 2017
May 31, 2017
Derivative [Line Items]      
Fair value of underlying stock $ 0.78 $ 0.59 $ 0.60
Risk free rate 1.20% 2.08% 1.71%
Expected term (in years) 5 years 3 years 9 months 14 days 4 years 3 months 15 days
Stock price volatility 106.00% 80.00% 94.00%
Expected dividend yield 0.00% 0.00% 0.00%
Probability of Fundamental Transaction 50.00% 50.00% 50.00%
Probability of holder requesting cash payment 50.00% 50.00% 50.00%