Stock Options and Stock Based Compensation - Additional Information (Detail) - USD ($)
|
12 Months Ended |
|
May 31, 2018 |
May 31, 2017 |
May 31, 2016 |
May 31, 2015 |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
| Expected dividend rate |
0.00%
|
|
|
|
| Stock-based compensation expense recognized |
$ 50,336
|
$ 79,765
|
$ 58,198
|
|
| Outstanding stock options, total |
318,332
|
360,000
|
147,500
|
332,500
|
| Vested and exercisable stock options |
282,497
|
|
|
|
| Non-vested shares |
35,835
|
|
|
|
| Weighted average exercise price |
$ 2.36
|
$ 2.28
|
$ 3.11
|
$ 3.68
|
| Additional stock-based compensation expense |
$ 10,503
|
|
|
|
| Weighted average period over which unrecognized compensation is expected to be recognized |
10 months 25 days
|
|
|
|
| Intrinsic value of outstanding options |
$ 0
|
$ 0
|
|
|
| Intrinsic value of exercisable options |
0
|
0
|
|
|
| Intrinsic value of options exercised |
$ 0
|
$ 0
|
$ 0
|
|
| Maximum [Member] |
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
| Outstanding options expiration year |
2024
|
|
|
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| Grant date option one [Member] |
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|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
| Percentages of stock option granted |
50.00%
|
|
|
|
| Grant date Option two [Member] |
|
|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
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| Percentages of stock option granted |
25.00%
|
|
|
|
| Each anniversary option one [Member] |
|
|
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
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| Percentages of stock option granted |
16.70%
|
|
|
|
| Each anniversary option two [Member] |
|
|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
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| Percentages of stock option granted |
25.00%
|
|
|
|
| Grant date option three [Member] |
|
|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
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| Percentages of stock option granted |
0.00%
|
|
|
|
| Each anniversary option three [Member] |
|
|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
| Percentages of stock option granted |
33.00%
|
|
|
|
| 1995 Plan [Member] |
|
|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
| Shares reserved for issuances |
400,000
|
|
|
|
| Expiry of stock option plan |
2005-12
|
|
|
|
| Additional option issued under stock option plan |
0
|
|
|
|
| 2004 Plan [Member] |
|
|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
| Shares reserved for issuances |
300,000
|
|
|
|
| Expiry of stock option plan |
2015-08
|
|
|
|
| Additional option issued under stock option plan |
0
|
|
|
|
| 2014 Plan [Member] |
|
|
|
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
|
| Shares reserved for issuances |
300,000
|
|
|
|