Statements of Cash Flows - Supplemental Cash Flows and Non Cash Investing and Financing Activities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 25, 2014	Jul. 26, 2013
Non-cash Investing and Financing Activities:
Capital expenditures incurred but not paid	$ 11.5	$ 17.7
Acquisition of software through long-term financing	3.1	10.6
Supplemental Cash Flow Information:
Income taxes paid, net of refunds	68.2	19.1
Interest paid, net of capitalized interest	$ 11.7	$ 23.0