Number of stock option plans.

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Percentage of stock outperform in order for target award to vest.

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Share based compensation arrangement by share based payment award award exercisable period.

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Share based compensation arrangement by share based payment award percentage of award achieved.

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Share based compensation arrangement by share based payment award performance period.

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Share based compensation percentage of target award granted for calculating maximum aggregate award of performance share.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

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Gross value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP). Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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Amount of stock repurchase plan authorized.

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Number of shares that have been repurchased during the period and are being held in treasury.

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Stockholders' Equity - Additional Information (Detail)	6 Months Ended		12 Months Ended
Stockholders' Equity - Additional Information (Detail)	Oct. 31, 2016 USD ($) OptionPlan shares	Oct. 31, 2015 USD ($) shares	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase authorization \| $	$ 50,000,000
Repurchase of common stock	0
Number of stock option plans \| OptionPlan	2
Intrinsic value of stock outstanding \| $	$ 7,900,000	$ 19,300,000
Intrinsic value of stock exercisable \| $	7,900,000	19,300,000
Intrinsic value of stock exercised \| $	0	$ 1,900,000
Unrecognized compensation cost of outstanding options \| $	$ 0
Shares issued under employee stock purchase plan	66,812	92,249
Stock-based compensation expense \| $	$ 3,900,000	$ 3,200,000
Performance period	3 years
Percentage of maximum aggregate award granted	200.00%
Percentage of stock outperform in order for target award to vest			5.00%	5.00%	10.00%
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded	225,634
Stock units, forfeited	15,006
RSUs \| Without Market Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded		198,471
RSUs \| Non-Executive Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded	170,738
RSUs \| Non-Executive Employees \| Without Market Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded		162,092
RSUs \| Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded	24,896
RSUs \| Director \| Without Market Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded		36,379
RSUs \| Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded	30,000
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded	118,500	104,000
Share based payment award percentage of award achieved	200.00%	173.30%
PSUs \| Non-Executive Employees \| Without Market Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, awarded		5,379
PSUs \| Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units, vested	237,000	180,231
RSUs and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense \| $	$ 3,600,000	$ 3,000,000
Stock units, awarded	344,134	280,081
Stock units, vested	363,702	320,950
Stock units, forfeited	15,006	72,123
Value of shares issued for vested awards \| $	$ 10,200,000	$ 5,300,000
Weighted average remaining contractual term	1 year 8 months 12 days
Unrecognized compensation cost related to unvested RSUs and PSUs \| $	$ 9,700,000
2013 Incentive Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of award vested exercisable	10 years
2013 Incentive Stock Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period to award vested and calculate volatility rate	3 years
2013 Incentive Stock Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period to award vested and calculate volatility rate	4 years