Auction Rate Securities - Additional Information (Detail)	3 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2016 USD ($) institution	Jul. 31, 2016 USD ($) institution	Oct. 31, 2015 USD ($) institution
Schedule of Available-for-sale Securities
Number of financial institution | institution	2	2	3
Auction rate securities	$ 5,000,000	$ 5,000,000
Interest rate reset interval		30 days
Auction Rate Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	8,000,000	$ 8,000,000	$ 13,000,000
Debt securities	10,000,000	10,000,000	15,000,000
Amortized cost basis	8,000,000	8,000,000	13,000,000
Gross unrealized gain (loss)	0
Unrealized holding gain (loss) on securities		0	0
Auction Rate Securities | Retained Earnings
Schedule of Available-for-sale Securities
Total amount of other-than-temporary impairment (OTTI) credit loss recognized	$ 2,000,000	$ 2,000,000	$ 2,000,000