Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative
Asset Derivatives Fair Value	$ 28.0	$ 10.8
Liability Derivatives Fair Value	92.9	135.6
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	28.0	10.8
Designated as Hedging Instrument | Other Liability
Derivative
Liability Derivatives Fair Value	60.4	133.7
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	5.7	9.2
Designated as Hedging Instrument | Interest Rate Swaps | Other Liability
Derivative
Liability Derivatives Fair Value	20.8	35.0
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	22.3	1.6
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liability
Derivative
Liability Derivatives Fair Value	39.6	98.7
Not Designated as Hedging Instrument | Other Liability
Derivative
Liability Derivatives Fair Value	82.4	55.1
Not Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liability
Derivative
Liability Derivatives Fair Value	31.3
Not Designated as Hedging Instrument | Credit Risk Contract | Other Liability
Derivative
Liability Derivatives Fair Value	1.2	1.9
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liability
Derivative
Liability Derivatives Fair Value	$ 49.9	$ 53.2