Restructuring and Other Charges - Activities Related to Restructuring Reserves (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 25, 2014	Jul. 26, 2013
Restructuring Cost and Reserve [Line Items]
Net charges	$ 0	$ 48.4
May 2013 Restructuring
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period		0
Net charges		48.4
Cash payments		(24.6)
Balance at end of period		23.8
March 2014 Restructuring
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period	26.5
Net charges	0
Cash payments	(21.6)
Balance at end of period	$ 4.9