Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Asset Derivatives Fair Value	$ 36.4	$ 81.6
Liability Derivatives Fair Value	137.6	170.5
Designated as Hedging Instrument | Other Long-term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	36.4	81.6
Designated as Hedging Instrument | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	137.0	170.5
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	35.7	76.5
Designated as Hedging Instrument | Interest Rate Swaps | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	37.5	31.7
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments
Derivative [Line Items]
Asset Derivatives Fair Value	0.7	5.1
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	99.5	138.8
Not Designated as Hedging Instrument | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	65.7
Not Designated as Hedging Instrument | Credit Default Swaps | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	0.6
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	$ 65.1	$ 83.9