Reconciliation of Liability Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($)	12 Months Ended
	May 31, 2018	May 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,323,732	$ 3,014,667
Fair value adjustments	(1,690,935)	(2,164,533)
Ending Balance	$ 1,323,732	3,014,667
Investor Warrants Issued with Registered Direct Equity Offering
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants issued		4,360,000
Placement Agent Warrants Issued with Registered Direct Equity Offering
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants issued		$ 819,200