Investments - Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Thousands	Jul. 28, 2018	Apr. 28, 2018
Summary of investments
Gross Unrealized Gains	$ 2,660	$ 2,243
Gross Unrealized Losses	(423)	(457)
Fair Value	56,762	59,354
Equity securities
Summary of investments
Gross Unrealized Gains	2,462	2,142
Gross Unrealized Losses	(44)	(39)
Fair Value	19,038	18,765
Fixed income
Summary of investments
Gross Unrealized Gains	29	29
Gross Unrealized Losses	(366)	(418)
Fair Value	33,587	36,312
Other
Summary of investments
Gross Unrealized Gains	169	72
Gross Unrealized Losses	(13)
Fair Value	$ 4,137	$ 4,277