Significant Assumptions Used to Determine Fair Value of Auction Rate Securities (Detail)	Jul. 31, 2012 Year	Oct. 31, 2011 Year
Schedule of Available-for-sale Securities [Line Items]
Yields	2.15%
Minimum
Schedule of Available-for-sale Securities [Line Items]
Discount rates	2.34%	3.21%
Yields	2.00%	2.00%
Average expected lives	4	4
Maximum
Schedule of Available-for-sale Securities [Line Items]
Discount rates	10.52%	17.50%
Yields	3.50%	3.50%
Average expected lives	10	10