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. 24, 2014	Oct. 25, 2013
Non-cash Investing and Financing Activities:
Capital expenditures incurred but not paid	$ 8.8	$ 27.1
Acquisition of software through long-term financing	12.3	11.4
Supplemental Cash Flow Information:
Income taxes paid, net of refunds	68.6	26.5
Interest paid	$ 11.9	$ 23.2