Significant Assumptions Used to Determine the Fair Value of Auction Rate Securities (Detail)	Jul. 31, 2011 Year	Oct. 31, 2010 Year
Minimum
Discount rates	2.31%	2.50%
Yields	2.00%	2.00%
Average expected lives	4	4
Maximum
Discount rates	20.23%	18.59%
Yields	3.50%	3.50%
Average expected lives	10	10