Investments - Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Thousands	Jan. 27, 2018	Apr. 29, 2017
Summary of investments
Gross Unrealized Gains	$ 2,680	$ 2,526
Gross Unrealized Losses	(334)	(163)
Fair Value	61,044	53,677
Equity securities
Summary of investments
Gross Unrealized Gains	2,565	1,796
Gross Unrealized Losses	(25)	(83)
Fair Value	19,094	13,610
Fixed income
Summary of investments
Gross Unrealized Gains	38	729
Gross Unrealized Losses	(309)	(72)
Fair Value	37,479	37,580
Mutual funds
Summary of investments
Fair Value	12	6
Other
Summary of investments
Gross Unrealized Gains	77	1
Gross Unrealized Losses		(8)
Fair Value	$ 4,459	$ 2,481