Stock-based Compensation - Summary of Weighted-Average Assumptions (Details) - $ / shares	12 Months Ended
Apr. 27, 2019	Apr. 28, 2018	Apr. 29, 2017
Director And Employee Stock Option Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	4.50%	2.20%	2.00%
Expected stock price volatility	24.60%	21.60%	21.20%
Risk-free interest rate	2.90%	1.90%	1.20%
Expected life (years)	6 years 2 months 12 days	6 years 7 months 6 days	6 years 7 months 6 days
Weighted average grant date fair value per share (in usd per share)	$ 3.66	$ 8.18	$ 8.32
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	5.20%	2.80%	2.30%
Expected stock price volatility	38.60%	28.10%	32.90%
Risk-free interest rate	2.50%	1.70%	0.70%
Expected life (years)	18 days	18 days	18 days
Weighted average grant date fair value per share (in usd per share)	$ 5.21	$ 8.73	$ 10.33
Capital Accumulation Plan (CAP)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield		2.80%	2.30%
Expected stock price volatility		24.40%	28.30%
Risk-free interest rate		1.80%	0.90%
Expected life (years)		1 year	1 year
Weighted average grant date fair value per share (in usd per share)		$ 12.98	$ 15.21

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://fasb.org/us-gaap/role/ref/legacyRef
-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=109197908&loc=d3e5070-113901

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-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=115993241&loc=d3e301413-122809

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