Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits at beginning of year	$ 9	$ 13	$ 11
Additions for tax positions provided in prior periods	2	1	2
Additions for tax positions provided in current period	0	0	1
Decreases for tax positions provided in prior years	(2)	(4)	(1)
Settlements of tax positions in the current period	0	(1)	0
Unrecognized tax benefits at end of year	$ 9	$ 9	$ 13

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

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

+ Details

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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