Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Feb. 29, 2012	Nov. 30, 2011
Fair Value, Inputs, Level 1
Fair Value, Measurement Inputs, Disclosure [Line Items]
Money market funds	$ 98.7
Fair Value, Inputs, Level 2
Fair Value, Measurement Inputs, Disclosure [Line Items]
Long-term debt excluding credit facilities, fair value	270.6	270.9
Long-term debt excluding credit facilities, carrying amount	$ 266.0	$ 266.2