Investments - Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Thousands	Oct. 27, 2018	Apr. 28, 2018
Summary of investments
Gross Unrealized Gains	$ 2,137	$ 2,243
Gross Unrealized Losses	(443)	(457)
Fair Value	54,285	59,354
Equity securities
Summary of investments
Gross Unrealized Gains	1,889	2,142
Gross Unrealized Losses	(99)	(39)
Fair Value	18,525	18,765
Fixed income
Summary of investments
Gross Unrealized Gains	27	29
Gross Unrealized Losses	(333)	(418)
Fair Value	31,339	36,312
Other
Summary of investments
Gross Unrealized Gains	221	72
Gross Unrealized Losses	(11)
Fair Value	$ 4,421	$ 4,277