Gains and Losses Recorded in Consolidated Statement of Income related to Derivative Instruments Not Formally Designated as Hedges (Detail) (Nondesignated, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Income	$ 4.4	$ 7.2	$ 1.3	$ (5.3)
Credit Default Swap Contracts | Others Operating Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Income	(0.6)	1.1	(2.5)	0.3
Forward Contracts | Others Operating Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Income				0.2
Foreign Exchange Contracts | Others Operating Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount Recognized in Income	$ 5.0	$ 6.1	$ 3.8	$ (5.8)