Derivatives Not Designated as Hedging Instruments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Other Financial Items, net
Interest Expense	0		0
Interest Income
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Nominal Volume	602.6		1,311.4
Interest Income
Not Designated as Hedging Instrument | Foreign Exchange Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Nominal Volume	602.6	[1]	1,311.4	[2]
Other Financial Items, net	1.2		(2.5)
Interest Expense	0		0.10
Interest Income

[1] Net amount after deducting for offsetting swaps $532.8.

[2] Net amount after deducting for offsetting swaps $1,103.2.