Auction Rate Securities - Changes in Cost Basis and Fair Value of Auction Rate Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended			12 Months Ended		12 Months Ended
	Jul. 31, 2014		Jul. 31, 2013	Jul. 31, 2014		Jul. 31, 2013	Oct. 31, 2013 Cost Basis Auction rate securities	Jul. 31, 2014 Cost Basis Auction rate securities	Oct. 31, 2013 Fair Value, Inputs, Level 3 Auction rate securities	Jul. 31, 2014 Fair Value, Inputs, Level 3 Auction rate securities
Schedule of Available-for-sale Securities
Balance at beginning of year							$ 18.0	$ 13.0
Balance at beginning of year				13.0	[1]				17.8	13.0
Unrealized gains included in accumulated other comprehensive loss	0.5		0	0		0.2	0		0.2
Redemption of security by issuer							(5.0)		(5.0)
Balance at end of year							13.0	13.0
Balance at end of year	$ 13.0	[1]		$ 13.0	[1]				$ 13.0	$ 13.0

[1] For investments in auction rate securities, the fair values were based on discounted cash flow valuation models, primarily utilizing unobservable inputs. See Note 6, “Auction Rate Securities,” for the roll-forward of assets measured at fair value using significant unobservable Level 3 inputs and the sensitivity analysis of significant inputs.