Employee Stock Plans (Outstanding Stock Options And SARs) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Apr. 30, 2012 Year
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares	1,492
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	3.1
Options Outstanding, Weighted-Average Exercise Price	$ 14.00
Options Exercisable, Shares	1,061
Options Exercisable, Weighted-Average Remaining Contractual Life (in years)	2.4
Options Exercisable, Weighted-Average Exercise Price	$ 14.33
$ 6.26-$ 9.55 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 6.26
Range of Exercise Prices, Maximum	$ 9.55
Options Outstanding, Shares	312
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	0.9
Options Outstanding, Weighted-Average Exercise Price	$ 7.89
Options Exercisable, Shares	312
Options Exercisable, Weighted-Average Remaining Contractual Life (in years)	0.9
Options Exercisable, Weighted-Average Exercise Price	$ 7.89
$ 9.56-$13.90 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 9.56
Range of Exercise Prices, Maximum	$ 13.90
Options Outstanding, Shares	463
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	4.4
Options Outstanding, Weighted-Average Exercise Price	$ 11.23
Options Exercisable, Shares	148
Options Exercisable, Weighted-Average Remaining Contractual Life (in years)	4.1
Options Exercisable, Weighted-Average Exercise Price	$ 10.80
$13.91-$17.97 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 13.91
Range of Exercise Prices, Maximum	$ 17.97
Options Outstanding, Shares	352
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	3.5
Options Outstanding, Weighted-Average Exercise Price	$ 16.79
Options Exercisable, Shares	282
Options Exercisable, Weighted-Average Remaining Contractual Life (in years)	3.2
Options Exercisable, Weighted-Average Exercise Price	$ 17.26
$17.98-$24.08 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum	$ 17.98
Range of Exercise Prices, Maximum	$ 24.08
Options Outstanding, Shares	365
Options Outstanding, Weighted-Average Remaining Contractual Life (in years)	2.9
Options Outstanding, Weighted-Average Exercise Price	$ 20.02
Options Exercisable, Shares	319
Options Exercisable, Weighted-Average Remaining Contractual Life (in years)	2.5
Options Exercisable, Weighted-Average Exercise Price	$ 19.66

Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average remaining life of the exercisable stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ 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 (e)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(a, b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

+ 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 (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted-average period remaining as of the balance sheet date until option expiration pertaining to the outstanding stock options for all option plans in the customized range of exercise prices, which may be expressed in a variety of ways (for example, years, months).

+ 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 (e)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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