Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Aug. 31, 2012	Nov. 30, 2011
Fair Value, Inputs, Level 1
Fair Value, Measurement Inputs, Disclosure [Line Items]
Money market funds	$ 55.4
Fair Value, Inputs, Level 2
Fair Value, Measurement Inputs, Disclosure [Line Items]
Long-term debt excluding credit facilities, fair value	181.0	270.9
Long-term debt excluding credit facilities, carrying amount	$ 178.7	$ 266.2