Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended
Jul. 31, 2017	Jul. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Option for common stock	872,000	333,000
Stock-based compensation expense	$ 316,000	$ 388,000
Income tax benefit	$ 139,000	$ 145,000
Stock options exercised	101,516	223,276
Total intrinsic value of options exercised	$ 207,000	$ 856,000
Unrecognized compensation cost related to unvested stock option	$ 3,400,000
Weighted average period for Unrecognized compensation cost	1 year 8 months 5 days

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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- Definition

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.

+ References

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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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Number of share options (or share units) exercised during the current period.

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