Summary of the Available-for-Sale Securities' Gross Unrealized Losses and Fair Value (Detail) (Available-for-Sale Securities Unrealized Loss Positions, USD $) In Thousands	Jul. 31, 2010
Investments, Unrealized Loss Position [Line Items]
Less Than 12 Months Gross Unrealized Holding Losses	$ (805)	[1]
Less Than 12 Months Fair Value	54,959	[1]
Greater Than or Equal to 12 Months Gross Unrealized Holding Losses	(10,090)	[1]
Greater Than or Equal to 12 Months Fair Value	61,747	[1]
ARS | Student Loan Backed
Investments, Unrealized Loss Position [Line Items]
Less Than 12 Months Gross Unrealized Holding Losses	(805)
Less Than 12 Months Fair Value	54,959
Greater Than or Equal to 12 Months Gross Unrealized Holding Losses	(9,384)
Greater Than or Equal to 12 Months Fair Value	47,453
Auction rate preferred securities
Investments, Unrealized Loss Position [Line Items]
Greater Than or Equal to 12 Months Gross Unrealized Holding Losses	(706)
Greater Than or Equal to 12 Months Fair Value	$ 14,294

[1] Fair value excludes $58.0 million as of July 31, 2010 of securities whose fair value approximated par. Additionally, as of July 31, 2010, fair value shown above excludes ($2.2) million of OTTI that has been previously recognized in earnings.