Pension and Other Postretirement Benefits (Funded Status of Plans) (Details) - USD ($) $ in Millions	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Funded Status of Plans
Assets	$ 780	$ 623
Pension Benefits [Member]
Funded Status of Plans
Assets	780	623	$ 594
Obligations	(903)	(893)	(898)
Funded status	(123)	(270)
Medical and Life Insurance Benefits [Member]
Funded Status of Plans
Assets	0	0	0
Obligations	(50)	(52)	$ (56)
Funded status	$ (50)	$ (52)

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

+ Details

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- Definition

Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) 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 (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919

+ Details

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- References

No definition available.

+ Details

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- Details

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- Details

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