Debt (Details) € in Millions, £ in Millions, $ in Millions	Jul. 31, 2016 EUR (€)	Jul. 31, 2016 GBP (£)	Jul. 31, 2016 USD ($)	Apr. 30, 2016 USD ($)
Debt Instrument [Line Items]
Long-term debt			$ 1,953	$ 1,230
One Point Zero Percent Notes Due in Fiscal Two Thousand Eighteen [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 250	$ 250
Debt Instrument, Interest Rate, Stated Percentage	1.00%	1.00%	1.00%	1.00%
Long-term debt, including current portion			$ 249	$ 249
Two Point Two Five Percent Notes Due in Fiscal Two Thousand Twenty Three [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 250	$ 250
Debt Instrument, Interest Rate, Stated Percentage	2.25%	2.25%	2.25%	2.25%
Long-term debt, including current portion			$ 248	$ 248
One Point Two Percent Notes Due in Fiscal Two Thousand Twenty Seven [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	€ 300		$ 335	$ 0
Debt Instrument, Interest Rate, Stated Percentage	1.20%	1.20%	1.20%	1.20%
Long-term debt, including current portion			$ 332	$ 0
Two Point Six Percent Notes Due in Fiscal Two Thousand Twenty Nine [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		£ 300	$ 397	$ 0
Debt Instrument, Interest Rate, Stated Percentage	2.60%	2.60%	2.60%	2.60%
Long-term debt, including current portion			$ 391	$ 0
Three Point Seven Five Percent Notes Due in Fiscal Two Thousand Forty Three [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 250	$ 250
Debt Instrument, Interest Rate, Stated Percentage	3.75%	3.75%	3.75%	3.75%
Long-term debt, including current portion			$ 248	$ 248
Four Point Five Percent Notes Due in Fiscal Two Thousand Forty Six [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 500	$ 500
Debt Instrument, Interest Rate, Stated Percentage	4.50%	4.50%	4.50%	4.50%
Long-term debt, including current portion			$ 485	$ 485

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
-Paragraph 1
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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Section S99
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