Derivative Financial Instruments - Effect of Derivative Instruments in Cash Flow Hedging Relationships on Condensed Consolidated Statements of Income and Other Comprehensive Income (OCI) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive loss expected to be reclassified into earnings			$ (2,885)
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive loss expected to be reclassified into earnings	$ (702)	$ (702)	$ (2,107)	$ (2,099)