Pension and Other Postretirement Benefits (Assumptions and Sensativity) (Details)	12 Months Ended
Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Pension Benefits [Member]
Assumptions used in computing benefit plan obligations
Discount rate (percent)	4.09%	4.46%
Rate of salary increase (percent)	4.00%	4.00%
Assumptions used in computing benefit plan expense
Discount rate (percent)	4.46%	4.08%	4.92%
Rate of salary increase (percent)	4.00%	4.00%	4.00%
Expected return on plan assets (percent)	7.50%	7.50%	7.75%
Medical and Life Insurance Benefits [Member]
Assumptions used in computing benefit plan obligations
Discount rate (percent)	4.09%	4.67%
Assumptions used in computing benefit plan expense
Discount rate (percent)	4.67%	4.36%	4.84%
Present rate before age 65 [Member] \| Medical and Life Insurance Benefits [Member]
Assumed health care cost trend rates
Present rate (percent)	7.50%	7.75%
Present rate age 65 and after [Member] \| Medical and Life Insurance Benefits [Member]
Assumed health care cost trend rates
Present rate (percent)		6.75%

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The interest rate used to adjust for the time value of money for the plan.

+ References

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- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

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- Definition

The interest rate used to adjust for the time value of money.

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

Expected rate of compensation increases (for pay-related plans).

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- Definition

The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

+ 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 (l)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Health Care Cost Trend Rate

-URI http://asc.fasb.org/extlink&oid=6514820

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