Summary of Fair Value Warrant Derivative Liability and Related Common Shares (Detail) - USD ($)		Feb. 28, 2018	May 31, 2017	Sep. 15, 2016
Derivative [Line Items]
Derivative liability	[1]	$ 3,288,799	$ 3,014,667
Registered Direct Equity Offering | Investor Warrants Issued with Registered Direct Equity Offering
Derivative [Line Items]
Shares indexed		7,733,334	7,733,334	7,733,334
Derivative liability		$ 3,288,799	$ 3,014,667	$ 5,179,200

[1] The Company did not have any assets or liabilities measured at fair value using Level 1 or 2 of the fair value hierarchy as of February 28, 2018 and May 31, 2017.