Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Derivative
Asset Derivatives Fair Value	$ 39.3	$ 28.0
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	39.3	28.0
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	42.4	60.4
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	4.8	5.7
Designated as Hedging Instrument | Interest Rate Swaps | Other Liabilities
Derivative
Liability Derivatives Fair Value	17.4	20.8
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	34.5	22.3
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	25.0	39.6
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	88.1	82.4
Not Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	31.0	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	$ 55.8	$ 49.9