Investments - Held-To-Maturity Securities (Details) - USD ($) $ in Thousands	Jan. 25, 2020	Apr. 30, 2019
Held To Maturity Securities
Amortized Cost	$ 156,764	$ 159,873
Gross Unrealized Gains	136	100
Gross Unrealized Losses	(4)	(58)
Total	156,896	159,915
Municipal securities
Held To Maturity Securities
Amortized Cost	23,452	5,332
Gross Unrealized Gains	12	2
Gross Unrealized Losses	(4)	(1)
Total	23,460	5,333
U.S. government securities
Held To Maturity Securities
Amortized Cost	45,439	70,609
Gross Unrealized Gains	63	78
Gross Unrealized Losses		(52)
Total	45,502	70,635
Corporate bonds
Held To Maturity Securities
Amortized Cost	86,856	83,932
Gross Unrealized Gains	57	20
Gross Unrealized Losses		(5)
Total	86,913	$ 83,947
Certificates of deposit
Held To Maturity Securities
Amortized Cost	1,017
Gross Unrealized Gains	4
Total	$ 1,021

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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