v2.4.0.6
Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents $ 354.3 $ 581.7
Investments 145.6 132.4
Derivative assets 208.8 225.6
Total assets at fair value 708.7 939.7
Derivative liabilities (10.2) (15.6)
Total liabilities at fair value (10.2) (15.6)
Level 1
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 354.3 581.7
Investments 145.6 [1] 132.4 [1]
Derivative assets 137.3 [1] 154.5 [1]
Total assets at fair value 637.2 868.6
Level 2
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets 71.5 71.1
Total assets at fair value 71.5 71.1
Derivative liabilities (10.2) (15.6)
Total liabilities at fair value $ (10.2) $ (15.6)
[1] Includes long-term investments and derivatives that hedge market-driven changes in liabilities associated with the Company's supplemental benefit plans.