Financial Instruments and Fair Value Measurements - Summary of Investments (Detail) (USD $) In Millions, unless otherwise specified	Jan. 24, 2014	Apr. 26, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 3,142.8	$ 5,375.1
Gross Unrealized Gains	11.8	16.4
Gross Unrealized Losses	(2.2)	(3.3)
Estimated Fair Value	3,152.4	5,388.2
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,433.8	3,132.8
Gross Unrealized Gains	11.5	14.9
Gross Unrealized Losses	(0.7)	(0.6)
Estimated Fair Value	2,444.6	3,147.1
U.S. Treasury And Government Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	249.3	392.8
Gross Unrealized Gains	0.3	0.9
Gross Unrealized Losses	0	0
Estimated Fair Value	249.6	393.7
Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	237.2	178.5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	237.2	178.5
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	135.0	135.4
Gross Unrealized Gains	0	0.1
Gross Unrealized Losses	0	0
Estimated Fair Value	135.0	135.5
Money Market Funds
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	13.1	1,463.1
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	13.1	1,463.1
Auction Rate Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	41.9	44.2
Gross Unrealized Gains	0	0.5
Gross Unrealized Losses	(1.5)	(2.7)
Estimated Fair Value	40.4	42.0
Equity Funds
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	32.5	28.3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 32.5	$ 28.3