Financial Instruments - Contractual Maturities of Types of Securities (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2014
Cost
Due in 1 year	$ 375.2
Due in 1 year through 5 years	297.7
Due in 5 years through 10 years	0
Due after 10 years	0
Total	672.9
Fair Value
Due in 1 year	375.2
Due in 1 year through 5 years	297.5
Due in 5 years through 10 years	0
Due after 10 years	0
Total	$ 672.7