Debt and Credit Facilities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		9 Months Ended			3 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 5.25% Senior Notes due April 2023	Mar. 31, 2013 5.25% Senior Notes due April 2023	Dec. 31, 2012 5.25% Senior Notes due April 2023	Mar. 31, 2013 7.875% Senior Notes due June 2017
Debt Disclosure [Line Items]
Aggregate principal amount				$ 425
Debt interest rate			5.25%	5.25%	5.25%	7.875%
Aggregate repurchase price of senior notes						431
Early redemption						400
Premium paid on redemption of debt percentage						6.00%
Premium paid on redemption of debt						23
Accrued interest paid on redemption of debt						8
Recognized net pre-tax loss	(32.4)					32.0
Senior notes maturity date			Apr. 01, 2023			Jun. 01, 2017
Frequency of interest payments			Interest is payable on April 1 and October 1 of each year, commencing October 1, 2013
Short-term borrowings	$ 75.2	$ 39.2