Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 US Treasury Securities	Dec. 31, 2011 US Treasury Securities	Dec. 31, 2004 US Treasury Securities	Dec. 31, 2012 Minimum	Dec. 31, 2012 Maximum
Summary Of Significant Accounting Policies [Line Items]
Percentage of interest in joint ventures							20.00%	50.00%
Threshold for recognition in consolidated statements of income, percentage of fair value of plan assets or projected benefit obligations	10.00%
Smoothing period of asset gains and losses	5 years
Deferred costs associated with yearly planed major maintenance, amortization period	12 months
Definite-lived intangible assets useful life							3 years	50 years
Foreign exchange transaction gains (losses)	$ (4.9)	$ (3.6)	$ 1.0
Maximum remaining expiration period for foreign currency forward contracts	1 year
Notional value of outstanding foreign currency forward contracts	274.0	148.7
Notional value of treasury lock securities						275.0
Percentage of public offering of senior notes						85.00%
Treasury lock securities, yield						4.25%
Cumulative loss on treasury lock securities						2.2
Treasury lock securities, fixed rate				4.25%
Unrealized losses in accumulated other comprehensive loss, before tax				0.5	0.7
Unrealized losses in accumulated other comprehensive loss, after tax				$ 0.3	$ 0.4