Location and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Asset Derivatives Fair Value	$ 62.1	$ 81.6
Liability Derivatives Fair Value	157.4	170.5
Designated as Hedging Instrument | Other Long-term Investments [Member]
Derivative [Line Items]
Asset Derivatives Fair Value	62.1	81.6
Designated as Hedging Instrument | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	156.7	170.5
Designated as Hedging Instrument | Interest Rate Swap [Member] | Other Long-term Investments [Member]
Derivative [Line Items]
Asset Derivatives Fair Value	59.6	76.5
Designated as Hedging Instrument | Interest Rate Swap [Member] | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	31.2	31.7
Designated as Hedging Instrument | Foreign Exchange Contract [Member] | Other Long-term Investments [Member]
Derivative [Line Items]
Asset Derivatives Fair Value	2.5	5.1
Designated as Hedging Instrument | Foreign Exchange Contract [Member] | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	125.5	138.8
Not Designated as Hedging Instrument | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	78.2
Not Designated as Hedging Instrument | Credit Default Swap [Member] | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	0.7
Not Designated as Hedging Instrument | Embedded Derivative in Modified Coinsurance Arrangement | Other Liability
Derivative [Line Items]
Liability Derivatives Fair Value	$ 77.5	$ 83.9