Stock-based Compensation - Summary of Weighted-Average Assumptions (Details) - $ / shares	12 Months Ended
Apr. 30, 2016	Apr. 25, 2015	Apr. 26, 2014
Director And Employee Stock Option Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	1.80%	2.00%	1.80%
Expected stock price volatility	25.60%	26.30%	30.00%
Risk-free interest rate	2.10%	2.10%	1.50%
Expected life (years)	6 years 8 months 1 day	7 years	7 years 1 month 6 days
Weighted average grant date fair value per share (in usd per share)	$ 9.66	$ 9.78	$ 11.02
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	2.00%	1.60%	1.60%
Expected stock price volatility	21.10%	31.00%	31.00%
Risk-free interest rate	0.50%	0.10%	0.20%
Expected life (years)	7 months	6 months	6 months
Weighted average grant date fair value per share (in usd per share)	$ 9.16	$ 10.74	$ 9.46
Capital Accumulation Plan (CAP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	2.00%	1.60%	1.60%
Expected stock price volatility	19.70%	31.00%	31.00%
Risk-free interest rate	0.60%	0.30%	0.30%
Expected life (years)	1 year	1 year	1 year
Weighted average grant date fair value per share (in usd per share)	$ 14.13	$ 17.67	$ 15.00

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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