Fair Value Measurements - Hierarchy and Transfers (Details) - USD ($) $ in Thousands	Oct. 24, 2020	Apr. 25, 2020
Assets
Total assets	$ 50,388	$ 48,022
Recurring basis
Assets
Marketable securities	40,278	38,206
Held-to-maturity investments	2,531	3,337
Cost basis investments	7,579	6,479
Total assets	50,388	48,022
Liabilities
Contingent consideration liability	2,500
Recurring basis | Level 1
Assets
Marketable securities	0	0
Held-to-maturity investments	2,531	3,337
Cost basis investments	0	0
Total assets	2,531	3,337
Liabilities
Contingent consideration liability	0
Recurring basis | Level 2
Assets
Marketable securities	31,358	31,691
Held-to-maturity investments	0	0
Cost basis investments	0	0
Total assets	31,358	31,691
Liabilities
Contingent consideration liability	0
Recurring basis | Level 3
Assets
Marketable securities	0	0
Held-to-maturity investments	0	0
Cost basis investments	7,579	6,479
Total assets	7,579	6,479
Liabilities
Contingent consideration liability	2,500
Recurring basis | NAV
Assets
Marketable securities	8,920	6,515
Held-to-maturity investments	0	0
Cost basis investments	0	0
Total assets	8,920	$ 6,515
Liabilities
Contingent consideration liability	$ 0