Financial Instruments and Fair Value Measurements - Quantitative Information About Level Three Fair Value Measurements (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Jan. 24, 2014
Significant Unobservable Inputs (Level 3) | Auction Rate Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
ARSs Fair Value	$ 40.4
Minimum | Discounted Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Time-to-economic maturity	6 years 8 months 12 days
Illiquidity premium	1.50%
Coupon rate	1.10%
Minimum | Market Comparable Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	2.00%
Maximum | Discounted Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Time-to-economic maturity	10 years 7 months 6 days
Illiquidity premium	3.30%
Coupon rate	2.70%
Maximum | Market Comparable Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	4.00%
Weighted Average | Discounted Cash Flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Time-to-economic maturity	8 years 2 months 12 days
Illiquidity premium	2.30%
Coupon rate	1.90%
Weighted Average | Market Comparable Securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	2.80%