Significant Assumptions Used to Determine Fair Value of Auction Rate Securities (Detail)	Jan. 31, 2012 Year	Oct. 31, 2011 Year
Minimum
Discount rates	0.78%	3.21%
Yields	2.00%	2.00%
Average expected lives	4	4
Maximum
Discount rates	7.64%	17.50%
Yields	3.50%	3.50%
Average expected lives	10	10