Changes in Cost Basis and Fair Value of Auction Rate Securities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended
	Apr. 30, 2013		Apr. 30, 2012	Apr. 30, 2012	Oct. 31, 2012		Apr. 30, 2013 Cost Basis Auction Rate Securities	Oct. 31, 2012 Cost Basis Auction Rate Securities	Apr. 30, 2013 Fair Value, Inputs, Level 3 Auction Rate Securities	Oct. 31, 2012 Fair Value, Inputs, Level 3 Auction Rate Securities
Schedule of Available-for-sale Securities [Line Items]
Balance at beginning of year					$ 17,780	[1]	$ 17,994	$ 18,307	$ 17,780	$ 15,670
Unrealized gains included in accumulated other comprehensive loss									214	2,110
Redemption of security by issuer	(5,000)						(5,000)		(5,000)
Other-than-temporary credit loss recognized in earnings			313	313				(313)
Balance at ending of year	$ 12,994	[1]			$ 17,780	[1]	$ 12,994	$ 17,994	$ 12,994	$ 17,780

[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-forwards of assets measured at fair value using significant unobservable Level 3 inputs and the sensitivity analysis of significant inputs.