Financial Instruments and Fair Value Measurements - Quantitative Information About Level Three Fair Value Measurements (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Oct. 25, 2013
Significant Unobservable Inputs (Level 3) | Auction Rate Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
ARS Fair Value	$ 39.5
Minimum | Discounted Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Time-to-economic maturity	6 years 8 months 12 days
Liquidity risk premium, market credit spread and other factors	1.70%
Coupon rate	1.10%
Minimum | Market Comparable Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	2.20%
Maximum | Discounted Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Time-to-economic maturity	10 years 10 months 24 days
Liquidity risk premium, market credit spread and other factors	3.60%
Coupon rate	2.70%
Maximum | Market Comparable Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	9.20%
Weighted Average | Discounted Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Time-to-economic maturity	8 years 3 months 18 days
Liquidity risk premium, market credit spread and other factors	2.50%
Coupon rate	1.90%
Weighted Average | Market Comparable Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	5.40%