Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Derivative
Asset Derivatives Fair Value	$ 40.1	$ 49.8
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	40.1	49.8
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	25.0	18.3
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	5.3	2.4
Designated as Hedging Instrument | Interest Rate Swaps | Other Liabilities
Derivative
Liability Derivatives Fair Value	7.8	12.3
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	34.8	47.4
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	17.2	6.0
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	126.2	119.5
Not Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	32.9	31.6
Not Designated as Hedging Instrument | Credit Risk Contract | Other Liabilities
Derivative
Liability Derivatives Fair Value	0.1	0.3
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liabilities
Derivative
Liability Derivatives Fair Value	$ 93.2	$ 87.6