Employee 401(k) Savings Plan - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Apr. 28, 2018	Apr. 29, 2017	Apr. 30, 2016
Retirement Benefits [Abstract]
Employer matching contribution, percent	3.00%
Employer 401(k) contribution	$ 1.4	$ 1.3	$ 1.3

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration