Location and Fair Values of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivative
Asset Derivatives Fair Value	$ 32.7	$ 49.8
Designated as Hedging Instrument | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	32.7	49.8
Designated as Hedging Instrument | Other Liability
Derivative
Liability Derivatives Fair Value	20.3	18.3
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	0.0	2.4
Designated as Hedging Instrument | Interest Rate Swaps | Other Liability
Derivative
Liability Derivatives Fair Value	6.9	12.3
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative
Asset Derivatives Fair Value	32.7	47.4
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liability
Derivative
Liability Derivatives Fair Value	13.4	6.0
Not Designated as Hedging Instrument | Other Liability
Derivative
Liability Derivatives Fair Value	79.2	119.5
Not Designated as Hedging Instrument | Interest Rate Swaps | Other Liability
Derivative
Liability Derivatives Fair Value	0.7
Not Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liability
Derivative
Liability Derivatives Fair Value	31.4	31.6
Not Designated as Hedging Instrument | Credit Risk Contract | Other Liability
Derivative
Liability Derivatives Fair Value	0.4	0.3
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liability
Derivative
Liability Derivatives Fair Value	$ 46.7	$ 87.6