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Stockholders' Equity - Summary of Valuation Assumptions (Detail) - $ / shares
12 Months Ended
Apr. 27, 2018
Apr. 28, 2017
Apr. 29, 2016
Restricted Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 1.40% 1.00% 0.60%
Expected dividend yield 2.00% 3.10% 2.30%
RSUs granted, Weighted-Average Grant Date Fair Value $ 39.74 $ 24.99 $ 29.26
Employee Stock Purchase Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term in years 1 year 2 months 12 days 1 year 2 months 12 days 1 year 2 months 12 days
Risk-free interest rate 1.40% 0.80% 0.50%
Expected volatility 28.00% 30.00% 27.00%
Expected dividend yield 2.00% 3.10% 2.30%
RSUs granted, Weighted-Average Grant Date Fair Value $ 12.34 $ 7.85 $ 8.18