Financial Instruments And Fair Value (Contractual Maturities Of Available-For-Sale Securities) (Details) (USD $) In Millions, unless otherwise specified	Jan. 27, 2012
Financial Instruments And Fair Value [Abstract]
Due in one year or less, Cost	$ 821.6
Due in one year or less, Fair Value	823.6
Due in one through five years, Cost	1,672.0
Due in one through five years, Fair Value	1,675.8
Due after ten years, Cost	54.4	[1]
Due after ten years, Fair Value	51.0	[1]
Total, Cost	2,548.0
Total, Fair Value	$ 2,550.4

[1] Consists of auction rate securities which have contractual maturities of greater than 10 years.