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Commitments - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Oct. 31, 2012
Oct. 31, 2011
Oct. 31, 2010
Commitments [Abstract]      
Operating leases rental expenses $ 6.9 $ 6.0 $ 4.8
Minimum rentals to be received in the future under noncancelable subleases 1.9    
Purchase obligation for natural gas and aluminum $ 4.0 $ 2.8 $ 1.6