Auction Rate Securities - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2012 Entity	Jul. 31, 2012 Entity	Oct. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Number of different issuers the Company held investments in for auction rate securities	4	4
Investments in auction rate securities	$ 20,000,000	$ 20,000,000
Interest rate revising interval	30 days
Auction rate securities, earliest maturity period	2033	2033
Auction rate securities, latest maturity period	2050	2050
Investments in auction rate securities, estimated fair value	16,704,000	16,704,000	15,670,000
Auction rate securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value			10,700,000
Auction rate securities, Continuous Unrealized Loss Position, Less Than Twelve Months	11,700,000	11,700,000
Other-than-temporary impairment (OTTI) Credit loss recognized		300,000	1,700,000
Unrealized losses recorded in accumulated other comprehensive loss, before tax	1,300,000	1,300,000	2,600,000
Unrealized losses recorded in accumulated other comprehensive loss, net of taxes	800,000	800,000	1,600,000
Auction Rate Securities
Schedule of Available-for-sale Securities [Line Items]
Auction rate security, at fair value, that was not in unrealized loss position	5,000,000	5,000,000	5,000,000
Single Issuer Investment
Schedule of Available-for-sale Securities [Line Items]
Investments in auction rate securities	$ 5,000,000	$ 5,000,000