Pension and Other Postretirement Benefits (Funded Status of Plans) (Details) - USD ($) $ in Millions	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Funded Status of Plans
Assets	$ 623	$ 594
Pension Benefits [Member]
Funded Status of Plans
Assets	623	594	$ 626
Obligations	(893)	(898)	(887)
Funded status	(270)	(304)
Medical and Life Insurance Benefits [Member]
Funded Status of Plans
Assets	0	0	0
Obligations	(52)	(56)	$ (57)
Funded status	$ (52)	$ (56)

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Projected Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6522206

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accumulated Postretirement Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6503904

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Balance Type:	credit
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