Stockholders Equity - Accumulated Other Comprehensive Income (Loss) by Component Net of Tax (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 25, 2013	Oct. 26, 2012	Oct. 25, 2013	Oct. 26, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of April 26, 2013			$ 8.7
Other comprehensive income (loss) (OCI) before reclassifications			(2.7)
Amounts reclassified from AOCI			0.3
Other comprehensive income (loss)	7.6	3.0	(2.4)	3.3
Balance as of October 25, 2013	6.3		6.3
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of April 26, 2013			2.0
Other comprehensive income (loss) (OCI) before reclassifications			3.6
Amounts reclassified from AOCI			0
Other comprehensive income (loss)			3.6
Balance as of October 25, 2013	5.6		5.6
Defined Benefit Obligation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of April 26, 2013			(5.7)
Other comprehensive income (loss) (OCI) before reclassifications			0.2
Amounts reclassified from AOCI			0
Other comprehensive income (loss)			0.2
Balance as of October 25, 2013	(5.5)		(5.5)
Unrealized Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of April 26, 2013			11.4
Other comprehensive income (loss) (OCI) before reclassifications			(3.0)
Amounts reclassified from AOCI			(1.1)
Other comprehensive income (loss)			(4.1)
Balance as of October 25, 2013	7.3		7.3
Unrealized Gains (Losses) on Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance as of April 26, 2013			1.0
Other comprehensive income (loss) (OCI) before reclassifications			(3.5)
Amounts reclassified from AOCI			1.4
Other comprehensive income (loss)			(2.1)
Balance as of October 25, 2013	$ (1.1)		$ (1.1)