Investments - Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Thousands	Oct. 28, 2017	Apr. 29, 2017
Summary of investments
Gross Unrealized Gains	$ 2,422	$ 2,526
Gross Unrealized Losses	(161)	(163)
Fair Value	60,388	53,677
Equity securities
Summary of investments
Gross Unrealized Gains	2,303	1,796
Gross Unrealized Losses	(46)	(83)
Fair Value	19,079	13,610
Fixed income
Summary of investments
Gross Unrealized Gains	55	729
Gross Unrealized Losses	(115)	(72)
Fair Value	37,236	37,580
Mutual funds
Summary of investments
Fair Value	17	6
Other
Summary of investments
Gross Unrealized Gains	64	1
Gross Unrealized Losses		(8)
Fair Value	$ 4,056	$ 2,481