Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Derivative
Asset Derivatives Fair Value	$ 57.1	$ 28.0
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	57.1	28.0
Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	23.4	60.4
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	4.9	5.7
Designated as Hedging Instrument | Interest Rate Swaps | Other Liabilities
Derivative
Liability Derivatives Fair Value	12.9	20.8
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	52.2	22.3
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liabilities
Derivative
Liability Derivatives Fair Value	10.5	39.6
Not Designated as Hedging Instrument | Other Liabilities
Derivative
Liability Derivatives Fair Value	116.2	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	1.1	1.2
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liabilities
Derivative
Liability Derivatives Fair Value	$ 83.1	$ 49.9