Stockholders Equity - Accumulated Other Comprehensive Income (Loss) by Component Net of Tax (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 26, 2013	Jul. 27, 2012
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance as of April 26, 2013	$ 8.7
Other comprehensive income (loss) (OCI) before reclassifications	(8.9)
Amounts reclassified from AOCI	(1.1)
Other comprehensive income (loss)	(10.0)	0.3
Balance as of July 26, 2013	(1.3)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance as of April 26, 2013	2.0
Other comprehensive income (loss) (OCI) before reclassifications	(1.2)
Amounts reclassified from AOCI	0
Other comprehensive income (loss)	(1.2)
Balance as of July 26, 2013	0.8
Defined Benefit Obligation Adjustments
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance as of April 26, 2013	(5.7)
Other comprehensive income (loss) (OCI) before reclassifications	0.1
Amounts reclassified from AOCI	0
Other comprehensive income (loss)	0.1
Balance as of July 26, 2013	(5.6)
Unrealized Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance as of April 26, 2013	11.4
Other comprehensive income (loss) (OCI) before reclassifications	(7.4)
Amounts reclassified from AOCI	(0.1)
Other comprehensive income (loss)	(7.5)
Balance as of July 26, 2013	3.9
Unrealized Gains (Losses) on Derivative Instruments
Accumulated Other Comprehensive Income Loss Net Of Tax [Line Items]
Balance as of April 26, 2013	1.0
Other comprehensive income (loss) (OCI) before reclassifications	(0.4)
Amounts reclassified from AOCI	(1.0)
Other comprehensive income (loss)	(1.4)
Balance as of July 26, 2013	$ (0.4)