Shareholders' Equity - Summary of Stock Option Activity and Related Information for Stock Options Granted, Options Outstanding and Exercisable (Details) - Stock Options	12 Months Ended
	Apr. 29, 2017 $ / shares shares
2010 Stock Plan | $37.01
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in shares) | shares	72,000
Options outstanding - exercise price (in dollars per share) | $ / shares	$ 37.01
Options outstanding - avg remaining life	7 years 3 months 16 days
Options exercisable (in shares) | shares	48,000
Options exercisable - exercise price (in dollars per share) | $ / shares	$ 37.01
Options exercisable - avg. remaining life	7 years 3 months 16 days
2007 Stock Plan
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in shares) | shares	57,169
Options outstanding - exercise price (in dollars per share) | $ / shares	$ 31.82
Options exercisable (in shares) | shares	40,335
Options exercisable - exercise price (in dollars per share) | $ / shares	$ 29.65
2007 Stock Plan | $10.55
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in shares) | shares	5,000
Options outstanding - exercise price (in dollars per share) | $ / shares	$ 10.55
Options outstanding - avg remaining life	3 years 3 months 1 day
Options exercisable (in shares) | shares	5,000
Options exercisable - exercise price (in dollars per share) | $ / shares	$ 10.55
Options exercisable - avg. remaining life	3 years 3 months 1 day
2007 Stock Plan | $17.27
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in shares) | shares	8,333
Options outstanding - exercise price (in dollars per share) | $ / shares	$ 17.27
Options outstanding - avg remaining life	6 years 3 months 4 days
Options exercisable (in shares) | shares	8,333
Options exercisable - exercise price (in dollars per share) | $ / shares	$ 17.27
Options exercisable - avg. remaining life	6 years 3 months 4 days
2007 Stock Plan | $37.01
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in shares) | shares	43,836
Options outstanding - exercise price (in dollars per share) | $ / shares	$ 37.01
Options outstanding - avg remaining life	7 years 3 months 16 days
Options exercisable (in shares) | shares	27,002
Options exercisable - exercise price (in dollars per share) | $ / shares	$ 37.01
Options exercisable - avg. remaining life	7 years 3 months 16 days