Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017	Apr. 28, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate	(170.00%)	23.20%	(20.90%)	31.90%
Income Tax [Line Items]
Tax Cuts And Jobs Act Of 2017,incomplete accounting, provisional income tax benefit	$ 77,256
Tax Cuts And Jobs Act Of 2017, incomplete accounting, change in tax rate, deferred taxes, provisional income tax expense	81,206
Tax Cuts And Jobs Act Of 2017, incomplete accounting, transition tax for unremitted foreign earnings	$ (3,950)
Scenario, Forecast
Income Tax [Line Items]
Blended income tax rate, percent					30.50%