Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Preferred Stock, Common Stock, Treasury Stock and Warrants Narrative) (Details)

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Stockholders' Equity (Preferred Stock, Common Stock, Treasury Stock and Warrants Narrative) (Details) - USD ($)
 1 Months Ended 3 Months Ended 9 Months Ended
Sep. 06, 2018
Dec. 24, 2018
Jan. 31, 2019
Jan. 31, 2019
Jan. 31, 2018
Jul. 19, 2018
Apr. 30, 2018
Stockholders Equity [Line Items]              
Preferred stock, shares authorized     10,000,000 10,000,000     10,000,000
Preferred stock, shares issued     0 0     0
Preferred stock, shares outstanding     0 0     0
Share issued in exercise of stock options       49,792      
Proceeds from stock options exercised       $ 110,143 $ 598,876    
Per share price     $ 0.001 $ 0.001     $ 0.001
Stock issuance costs paid by third parties       $ 30,000      
Compensation cost of unvested shares yet to be recognized, period of recognition       3 years      
Chief Financial Officer [Member]              
Stockholders Equity [Line Items]              
Compensation cost of unvested shares yet to be recognized, period of recognition 5 years            
Restricted Stock [Member]              
Stockholders Equity [Line Items]              
Restricted shares granted, value   $ 127,000          
Award vesting period   36 months          
Shares granted   24,672          
Vesting period   The restricted shares shall vest in three equal annual increments on December 24, 2019, December 24, 2020 and December 24, 2021.          
Restricted Stock [Member] | Chief Financial Officer [Member]              
Stockholders Equity [Line Items]              
Restricted shares granted 25,000            
Award vesting period 36 months            
Compensation cost of unvested shares yet to be recognized $ 180,000            
Compensation cost of unvested shares yet to be recognized, period of recognition 36 months            
Market price of company stock $ 7.15            
Restricted Stock [Member] | Director [Member]              
Stockholders Equity [Line Items]              
Officers compensation   $ 35,000          
Cashless Exercise of Stock Options [Member]              
Stockholders Equity [Line Items]              
Share issued in exercise of stock options       86,635      
Preferred Stock [Member]              
Stockholders Equity [Line Items]              
Preferred stock, shares authorized     10,000,000 10,000,000     10,000,000
Preferred stock, shares issued     0 0     0
Preferred stock, shares outstanding     0 0     0
Common Stock [Member]              
Stockholders Equity [Line Items]              
Share issued in exercise of stock options       49,792      
Proceeds from stock options exercised       $ 110,143      
Treasury stock repurchased           1,000,000  
Per share price           $ 7.40  
Sale of common stock per share price           $ 7.40  
Common Stock [Member] | Cashless Exercise of Stock Options [Member]              
Stockholders Equity [Line Items]              
Share issued in exercise of stock options       86,635      
Warrant [Member]              
Stockholders Equity [Line Items]              
Share issued in exercise of stock options     35,921 35,921      
Warrants issued       92,049      
Warrant exercise price     $ 5.85 $ 5.85      
Warrant term       5 years      
Warrant [Member] | Cashless Exercise of Stock Options [Member]              
Stockholders Equity [Line Items]              
Share issued in exercise of stock options     64,375 64,375