Fair Value Measurements - Hierarchy and Transfers (Details) - USD ($) $ in Thousands	Apr. 25, 2020	Apr. 27, 2019
Assets
Total assets	$ 48,022	$ 57,421
Recurring basis
Assets
Marketable securities	38,206	42,101
Held-to-maturity investments	3,337	3,341
Cost basis investments	6,479	11,979
Total assets	48,022	57,421
Liabilities
Contingent consideration liability		7,900
Recurring basis | Level 1
Assets
Marketable securities	0	5
Held-to-maturity investments	3,337	3,341
Cost basis investments	0	0
Total assets	3,337	3,346
Liabilities
Contingent consideration liability		0
Recurring basis | Level 2
Assets
Marketable securities	31,691	34,390
Held-to-maturity investments	0	0
Cost basis investments	0	0
Total assets	31,691	34,390
Liabilities
Contingent consideration liability		0
Recurring basis | Level 3
Assets
Marketable securities	0	0
Held-to-maturity investments	0	0
Cost basis investments	6,479	11,979
Total assets	6,479	11,979
Liabilities
Contingent consideration liability		7,900
Recurring basis | NAV
Assets
Marketable securities	6,515	7,706
Held-to-maturity investments	0	0
Cost basis investments	0	0
Total assets	$ 6,515	7,706
Liabilities
Contingent consideration liability		$ 0