Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative
Asset Derivatives Fair Value	$ 10.9	$ 10.8
Liability Derivatives Fair Value	117.7	135.6
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	10.9	10.8
Designated as Hedging Instrument | Other Liability
Derivative
Liability Derivatives Fair Value	115.7	133.7
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	8.1	9.2
Designated as Hedging Instrument | Interest Rate Swaps | Other Liability
Derivative
Liability Derivatives Fair Value	30.9	35.0
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	2.8	1.6
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liability
Derivative
Liability Derivatives Fair Value	84.8	98.7
Not Designated as Hedging Instrument | Other Liability
Derivative
Liability Derivatives Fair Value	46.7	55.1
Not Designated as Hedging Instrument | Credit Default Swaps | Other Liability
Derivative
Liability Derivatives Fair Value	2.0	1.9
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liability
Derivative
Liability Derivatives Fair Value	$ 44.7	$ 53.2