Stock-based Compensation Expense - Additional Information (Detail) - USD ($)
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1 Months Ended |
3 Months Ended |
24 Months Ended |
39 Months Ended |
Feb. 28, 2019 |
Apr. 30, 2019 |
Apr. 30, 2018 |
Jan. 31, 2017 |
Apr. 30, 2019 |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Options granted |
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50,000
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| Deferred Stock Units [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Awards granted |
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426,847
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| Market Based Options [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Options granted |
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0
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| Market Based Options [Member] | Former CEO [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Options granted |
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800,000
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| Fair value of options outstanding |
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$ 2,100
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| Service period required to be fulfilled |
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3 years
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| Reversal of stock-based compensation expense |
$ 500,000
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| Options and Deferred Stock Units [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based awards fair value |
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$ 600,000
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| Stock Options [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized |
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$ 1,300,000
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$ 1,300,000
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| Share based compensation arrangement by share based payment award expected weighted average recognition period |
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2 years 1 month 6 days
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| Restricted Stock Units and Deferred Stock Units [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized |
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$ 1,200,000
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1,200,000
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| Share based compensation arrangement by share based payment award expected weighted average recognition period |
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1 year 10 months 24 days
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| Performance Stock Units (PSUs) [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized |
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$ 100,000
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$ 100,000
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| Share based compensation arrangement by share based payment award expected weighted average recognition period |
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9 months 18 days
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| 2011 Compensation and Incentive Plan [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, Description |
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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.
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| Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent |
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100.00%
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| Share-based compensation arrangement by share based payment award, Option award expiration period |
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10 years
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| 2011 Compensation and Incentive Plan [Member] | Minimum [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by Share-based payment award, vesting period |
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1 year
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| 2011 Compensation and Incentive Plan [Member] | Maximum [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by Share-based payment award, vesting period |
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3 years
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| 2011 Compensation and Incentive Plan [Member] | Stock Compensation Plan |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, number of shares authorized |
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9,300,000
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9,300,000
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| Share-based compensation arrangement by share-based payment award, number of shares available for grant |
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3,322,669
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3,322,669
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| 2011 Compensation and Incentive Plan [Member] | Deferred Stock Units [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by Share-based payment award, vesting period |
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1 year
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| Two Thousand Fifteen Employee Stock Purchase Plan |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, number of shares available for grant |
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1,086,964
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1,086,964
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| Share-based compensation arrangement by share-based payment award, Description |
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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.
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| Percentage of stock to be purchased under the plan |
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85.00%
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| Shares purchased under ESPP |
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7,819
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9,421
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| Two Thousand Fifteen Employee Stock Purchase Plan | Maximum [Member] |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, number of shares authorized |
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1,150,000
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1,150,000
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