Summary of Cash Proceeds of Offering (Detail)  | 
12 Months Ended | 
|---|---|
| 
 May 31, 2018  
USD ($) 
 | |
| Stockholders Equity Note [Line Items] | |
| Gross proceeds from sale of common stock | $ 10,000,000 | 
| Placement agent fees and expenses | 1,010,000 | 
| Total net proceeds | $ 8,990,000 | 
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- Definition Proceeds From Issuance Of Common Stock Gross No definition available. 
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- Definition Stockholders Equity Note [Line Items] No definition available. 
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- Definition The cash outflow for cost incurred directly with the issuance of an equity security. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition The cash inflow from the additional capital contribution to the entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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