Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.8.0.1
Stockholders' Equity - Additional Information (Detail) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 34 Months Ended
Jul. 13, 2017
Apr. 06, 2016
Jul. 31, 2015
Apr. 30, 2018
Apr. 30, 2018
CEO [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Market based options granted   600,000   800,000  
Chief Operating Officer [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Market based options granted       200,000  
Officer [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, options, vested in period, fair value       $ 2.1  
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized       $ 0.1 $ 0.1
Share-based compensation arrangement by share-based payment award, options, vested in period       9 months 18 days  
Compensation and Incentive Plan 2011 [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, number of additional shares authorized 4,000,000        
Share-based compensation arrangement by share-based payment award, Description       Option awards may be granted to employees at an exercise price per share of not less than 100% of the fair market value per common share on the date of the grant  
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent       100.00%  
Share-based compensation arrangement by share based payment award, Option award expiration period       10 years  
Compensation and Incentive Plan 2011 [Member] | Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by Share-based payment award, Option award vesting period       1 year  
Compensation and Incentive Plan 2011 [Member] | Maximum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by Share-based payment award, Option award vesting period       4 years  
Compensation and Incentive Plan 2011 [Member] | Stock Compensation Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, number of shares available for grant       2,529,993 2,529,993
Long Term Incentive Program [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by Share-based payment award, Option award vesting period       3 years  
2015 Employee Stock Purchase Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, Description     On each purchase date, eligible employees will purchase our stock at a price per share equal to 85% of the closing price of our common stock on the exercise date, but no less than par value.    
Maximum payroll deductions at base compensation under employee stock purchase plan     15.00%    
Minimum payroll deductions at base compensation under employee stock purchase plan     1.00%    
Offering period commence date     Oct. 01, 2015    
Percentage of stock to be purchased under the plan     85.00%    
Shares purchased under ESPP         51,844
2015 Employee Stock Purchase Plan [Member] | Maximum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, number of shares authorized     1,150,000