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Auction Rate Securities - Additional Information (Detail)
3 Months Ended 12 Months Ended
Jan. 31, 2017
USD ($)
institution
Oct. 31, 2016
USD ($)
institution
Schedule of Available-for-sale Securities    
Number of financial institution | institution 2 2
Interest rate reset interval 30 days  
Auction Rate Securities    
Schedule of Available-for-sale Securities    
Debt securities $ 10,000,000 $ 10,000,000
Amortized cost basis 8,000,000 8,000,000
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