Derivatives Not Designated as Hedging Instruments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Other Financial Items, net
Interest Expense	0		0		0		0
Interest Income
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Nominal Volume	512.1		1,272.8		512.1		1,272.8
Interest Income
Not Designated as Hedging Instrument | Foreign Exchange Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Nominal Volume	512.1	[1]	1,272.8	[1]	512.1	[1]	1,272.8	[1]
Other Financial Items, net	0.3		1.4		0.3		(8.5)
Interest Expense	0		0		0		0
Interest Income

[1] Net amount after deducting for offsetting swaps $468.3 million.