Contractual Maturities of Types of Securities (Detail) (USD $) In Millions	Jul. 31, 2011
Investments Classified by Contractual Maturity Date [Line Items]
Due in 1 year	$ 207.8
Due in 1 year through 5 years	187.4
Due in 5 years through 10 years
Due after 10 years	4.2
Total	399.4
Due in 1 year	208.0
Due in 1 year through 5 years	189.5
Due in 5 years through 10 years
Due after 10 years	4.2
Total	$ 401.7

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