Pensions and Other Postretirement Benefits (Details 8) (Significant Unobservable Inputs (Level 3) [Member], USD $) In Thousands	12 Months Ended
Apr. 30, 2011
Change in plan assets:
Fair value of plan assets at beginning of year	$ 44,779
Actual return on plan assets still held at reporting date	4,436
Purchases	6,200
Fair value of plan assets at end of year	55,415
U.S. Equity Securities [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	2,391
Actual return on plan assets still held at reporting date	698
Purchases	1,688
Fair value of plan assets at end of year	4,777
Hedge Funds [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	33,163
Actual return on plan assets still held at reporting date	1,988
Purchases	2,300
Fair value of plan assets at end of year	37,451
Private Equity Funds [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	9,225
Actual return on plan assets still held at reporting date	1,750
Purchases	2,212
Fair value of plan assets at end of year	$ 13,187

Actual return on plan assets, separately identifying the amount related to assets still held at the reporting date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph d(iv)(b)(i)

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those nonbenefit obligations may be considered as reductions of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph b

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph d(iv)(b)(i)

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 49

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- Definition

Purchases, sales, and settlements of plan assets that occurred during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph d(iv)(b)(ii)

+ Details

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