Components of Net Periodic Benefit Costs (Detail) (Deferred Compensation Plan, USD $) In Thousands, unless otherwise specified	12 Months Ended
Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Deferred Compensation Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2,566	$ 2,868	$ 3,346
Amortization of actuarial loss	3,111	2,357	1,374
Net periodic benefit cost	$ 5,677	$ 5,225	$ 4,720

The amount of gains or losses recognized in net periodic benefit cost.

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- Details

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(2)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

+ Details

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- Definition

The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

+ References

+ Details

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