Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Designated as Hedging Instrument | Other Long-term Investments [Member]
Derivative [Line Items]
Asset Derivatives Fair Value	$ 81.6	$ 137.7
Designated as Hedging Instrument | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	170.5	173.7
Designated as Hedging Instrument | Interest Rate Swaps | Other Long-term Investments [Member]
Derivative [Line Items]
Asset Derivatives Fair Value	76.5	134.2
Designated as Hedging Instrument | Interest Rate Swaps | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	31.7	32.9
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Long-term Investments [Member]
Derivative [Line Items]
Asset Derivatives Fair Value	5.1	3.5
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	138.8	140.8
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	$ 83.9	$ 135.7