Statements of Cash Flows - Supplemental Cash Flows and Non Cash Investing and Financing Activities (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Oct. 25, 2013	Oct. 26, 2012
Non-cash Investing and Financing Activities:
Reclassification of equity component of Convertible Notes	$ 0	$ 62.6
Acquisition of property and equipment outstanding in accounts payable	27.1	20.0
Acquisition of software through long-term financing	11.4	0.8
Supplemental Cash Flow Information:
Income taxes paid, net of refunds	26.5	26.5
Interest paid, net of capitalized interest	$ 23.2	$ 11.3