Shareholders' Equity - Summary of Stock Option Activity and Related Information for Stock Options Granted (Details) - Stock Options - $ / shares	12 Months Ended
Apr. 29, 2017	Apr. 30, 2016	May 02, 2015
2010 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding - beginning balance (in shares)	197,332	242,667	420,001
Awarded (in shares)	0	0	108,000
Exercised (in shares)	(125,332)	(18,668)	(285,334)
Cancelled (in shares)	0	(26,667)	0
Outstanding - ending balance (in shares)	72,000	197,332	242,667
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Wtd. Avg. Exercise Price, Outstanding - beginning balance (in dollars per share)	$ 24.55	$ 24.50	$ 11.75
Wtd. Avg. Exercise Price, Awarded (in dollars per share)	0.00	0.00	37.01
Wtd. Avg. Exercise Price, Exercised (in dollars per share)	17.40	12.96	10.47
Wtd. Avg. Exercise Price, Cancelled (in dollars per share)	0.00	32.07	0.00
Wtd. Avg. Exercise Price, Outstanding - ending balance (in dollars per share)	$ 37.01	$ 24.55	$ 24.50
2007 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding - beginning balance (in shares)	79,666	108,000	172,359
Awarded (in shares)	0	0	50,500
Exercised (in shares)	(22,497)	(28,334)	(114,859)
Cancelled (in shares)	0	0	0
Outstanding - ending balance (in shares)	57,169	79,666	108,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Wtd. Avg. Exercise Price, Outstanding - beginning balance (in dollars per share)	$ 28.91	$ 24.21	$ 10.02
Wtd. Avg. Exercise Price, Awarded (in dollars per share)	0.00	0.00	37.01
Wtd. Avg. Exercise Price, Exercised (in dollars per share)	21.52	10.99	8.55
Wtd. Avg. Exercise Price, Cancelled (in dollars per share)	0.00	0.00	0.00
Wtd. Avg. Exercise Price, Outstanding - ending balance (in dollars per share)	$ 31.82	$ 28.91	$ 24.21

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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