Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Designated as Hedging Instrument | Other Long term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	$ 108.2	$ 137.7
Designated as Hedging Instrument | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	182.5	173.7
Designated as Hedging Instrument | Interest Rate Swaps and Forwards | Other Long term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	101.3	134.2
Designated as Hedging Instrument | Interest Rate Swaps and Forwards | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	33.3	32.9
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	6.9	3.5
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	149.2	140.8
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	$ 107.0	$ 135.7