Stockholders Equity - Reconciliation of Retained Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 24, 2014	Jan. 25, 2013	Jan. 24, 2014	Jan. 25, 2013
Retained Earnings Adjustments [Line Items]
Beginning balance			$ 2,896.8
Net income	192.1	158.1	440.5	331.5
Repurchases of common stock			(1,507.0)
Dividends			(153.1)	0
Ending balance	0		0
Retained Earnings
Retained Earnings Adjustments [Line Items]
Repurchases of common stock			(921.3)
Retirement of treasury stock			(2,313.3)
Dividends			$ (102.7)