Income Taxes - Summary of Change in Valuation Allowances Against Deferred Income Taxes (Detail) - USD ($) $ in Thousands		12 Months Ended
		Apr. 29, 2018	Apr. 30, 2017	May 01, 2016
Valuation Allowance [Line Items]
beginning balance		$ 536	$ 590	$ 922
establishment of valuation allowance	[1]	4,550
ending balance		5,204	536	590
Valuation Allowance, Deferred Income Taxes [Member]
Valuation Allowance [Line Items]
change in estimate	[2]	$ 118	$ (54)	$ (332)

[1] The establishment of this valuation allowance pertains to U.S. foreign tax credits that are more-likely-than not to be realized as a result of the Tax Act.

[2] Amounts pertain to a change in estimate of the recoverability of certain deferred income tax assets as of the end of the respective prior fiscal year.