Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Designated as Hedging Instrument | Other Long term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	$ 118.4	$ 137.7
Designated as Hedging Instrument | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	165.7	173.7
Designated as Hedging Instrument | Interest Rate Swaps and Forwards | Other Long term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	113.2	134.2
Designated as Hedging Instrument | Interest Rate Swaps and Forwards | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	33.0	32.9
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	5.2	3.5
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	132.7	140.8
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liabilities
Derivative [Line Items]
Liability Derivatives Fair Value	$ 126.7	$ 135.7