Investments - Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Thousands	Jan. 28, 2017	Apr. 30, 2016
Summary of investments
Gross Unrealized Gains	$ 1,530	$ 1,408
Gross Unrealized Losses	(224)	(165)
Fair Value	49,645	46,976
Equity securities
Summary of investments
Gross Unrealized Gains	1,467	1,231
Gross Unrealized Losses	(98)	(135)
Fair Value	13,257	8,150
Fixed income
Summary of investments
Gross Unrealized Gains	62	176
Gross Unrealized Losses	(118)	(9)
Fair Value	33,972	36,527
Mutual funds
Summary of investments
Fair Value	10
Other
Summary of investments
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(8)	(21)
Fair Value	$ 2,406	$ 2,299