Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jan. 27, 2018	Apr. 29, 2017
Assets:
Cash equivalents	$ 3,401	$ 6,798
Deferred purchase price receivable	137,054	119,798
Derivative instruments	1,061	1,188
Total assets	141,516	127,784
Liabilities:
Derivative instruments	1,061	1,188
Fair Value, Inputs, Level 1
Assets:
Cash equivalents	3,401	6,798
Deferred purchase price receivable	0	0
Derivative instruments	0	0
Total assets	3,401	6,798
Liabilities:
Derivative instruments	0	0
Fair Value, Inputs, Level 2
Assets:
Cash equivalents	0	0
Deferred purchase price receivable	0	0
Derivative instruments	1,061	1,188
Total assets	1,061	1,188
Liabilities:
Derivative instruments	1,061	1,188
Fair Value, Inputs, Level 3
Assets:
Cash equivalents	0	0
Deferred purchase price receivable	137,054	119,798
Derivative instruments	0	0
Total assets	137,054	119,798
Liabilities:
Derivative instruments	$ 0	$ 0