Treasury Stock (Detail) - Schedule of Authorizations made by Board of Directors to repurchase Common Stock (USD $) In Millions, unless otherwise specified	1 Months Ended						48 Months Ended
	Nov. 30, 2010	Dec. 31, 2009	Feb. 28, 2009	Nov. 30, 2008	May 31, 2008	Dec. 31, 2007	Nov. 30, 2011
Authorization amount	$ 44.0	$ 20.0	$ 5.0	$ 10.0	$ 20.0	$ 20.0	$ 119.0
Less Repurchases made from December 2007 to November 2011							(80.1)
Remaining Board Authorization at November 30, 2011							$ 38.9