Derivative Instruments and Fair Value Measurement of Assets and Liabilities Derivative Instruments and Fair Value Measurement of Assets and Liabilities Narrative (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2013	Oct. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure	$ 4.2	$ 4.2
Quanex Screens [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Acquisition, Contingent Consideration, at Fair Value	$ 0.3