Annual report pursuant to Section 13 and 15(d)

Convertible Instruments - Long-term Convertible Note - June 2018 Note (Detail)

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Convertible Instruments - Long-term Convertible Note - June 2018 Note (Detail)
$ / shares in Units, shares in Millions
12 Months Ended
Nov. 15, 2018
USD ($)
$ / shares
Jun. 26, 2018
USD ($)
$ / shares
May 31, 2021
USD ($)
shares
May 31, 2020
USD ($)
shares
May 31, 2019
USD ($)
shares
Debt Instrument [Line Items]          
Net Proceeds     $ 100,000,000 $ 15,000,000 $ 14,877,000
Convertible note, redeemed amount     $ 77,703,000 15,092,000 1,680,000
Debt instrument converted number of shares issued | shares     19.9    
Long Term Convertible Note June 2018          
Debt Instrument [Line Items]          
Debt instrument term   2 years      
Convertible note, aggregate principal   $ 5,700,000      
Net Proceeds   $ 5,000,000.0      
Convertible notes, interest rate   10.00%      
Conversion price per share | $ / shares $ 0.55 $ 0.55      
Debt instrument lock in period   6 months      
Number of days of notice to be given for conversion of notes into common stock   5 days      
Number of days of notice to be given for redemption   5 days      
Conversion price ratio   1.5      
Days prior to conversion 20 days        
Stock price multiplier 0.85%        
Loss on extinguishment of convertible notes $ 1,500,000        
Net carrying value of note 5,400,000   $ 0 0  
Fair value of note 6,900,000        
Interest expense       400,000 400,000
Convertible note, redeemed amount       $ 4,500,000 $ 1,500,000
Debt instrument converted number of shares issued | shares       8.5 3.8
Cash paid to redeem debt       $ 500,000  
Long Term Convertible Note June 2018 | Maximum          
Debt Instrument [Line Items]          
Specified monthly redemption amount $ 350,000 $ 350,000