Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation Expense - Additional Information (Detail)

v3.19.1
Stock-based Compensation Expense - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 24 Months Ended 39 Months Ended
Feb. 28, 2019
Apr. 30, 2019
Apr. 30, 2018
Jan. 31, 2017
Apr. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Options granted   50,000      
Deferred Stock Units [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Awards granted   426,847      
Market Based Options [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Options granted         0
Market Based Options [Member] | Former CEO [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Options granted       800,000  
Fair value of options outstanding   $ 2,100      
Service period required to be fulfilled   3 years      
Reversal of stock-based compensation expense $ 500,000        
Options and Deferred Stock Units [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based awards fair value   $ 600,000      
Stock Options [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized   $ 1,300,000     $ 1,300,000
Share based compensation arrangement by share based payment award expected weighted average recognition period   2 years 1 month 6 days      
Restricted Stock Units and Deferred Stock Units [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized   $ 1,200,000     1,200,000
Share based compensation arrangement by share based payment award expected weighted average recognition period   1 year 10 months 24 days      
Performance Stock Units (PSUs) [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized   $ 100,000     $ 100,000
Share based compensation arrangement by share based payment award expected weighted average recognition period   9 months 18 days      
2011 Compensation and Incentive Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
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      
2011 Compensation and Incentive Plan [Member] | Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by Share-based payment award, vesting period   1 year      
2011 Compensation and Incentive Plan [Member] | Maximum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by Share-based payment award, vesting period   3 years      
2011 Compensation and Incentive Plan [Member] | Stock Compensation Plan          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, number of shares authorized   9,300,000     9,300,000
Share-based compensation arrangement by share-based payment award, number of shares available for grant   3,322,669     3,322,669
2011 Compensation and Incentive Plan [Member] | Deferred Stock Units [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by Share-based payment award, vesting period   1 year      
Two Thousand Fifteen Employee Stock Purchase Plan          
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   1,086,964     1,086,964
Share-based compensation arrangement by share-based payment award, Description   On each purchase date, eligible employees can 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.      
Percentage of stock to be purchased under the plan   85.00%      
Shares purchased under ESPP   7,819 9,421    
Two Thousand Fifteen Employee Stock Purchase Plan | 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     1,150,000