Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivative
Asset Derivatives Fair Value	$ 53.2	$ 28.0
Liability Derivatives Fair Value	71.8	92.9
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	53.2	28.0
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	38.5	60.4
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	5.6	5.7
Designated as Hedging Instrument | Interest Rate Swaps | Other Liabilities
Derivative
Liability Derivatives Fair Value	16.4	20.8
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	47.6	22.3
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	22.1	39.6
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	87.1	82.4
Not Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	32.0	31.3
Not Designated as Hedging Instrument | Credit Risk Contract | Other Liabilities
Derivative
Liability Derivatives Fair Value	1.3	1.2
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liabilities
Derivative
Liability Derivatives Fair Value	$ 53.8	$ 49.9