Quarterly report pursuant to Section 13 or 15(d)

Fair Value Of Financial Instruments (Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation) (Detail)

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Fair Value Of Financial Instruments (Fair Value, Assets Measured On Recurring Basis, Unobservable Input Reconciliation) (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]        
Balance $ 69.2 $ 68.1 $ 157.9 $ 45.6
Total gains        
Included in earnings 61.4 46.5 104.7 91.1
Included in other comprehensive income            
Settlements (46.7) (30.6) (178.7) (52.7)
Transfers into Level 3            
Transfers out of Level 3   (20.0)   (20.0)
Balance 83.9 64.0 83.9 64.0
Total gains for the period included in earnings attributable to the change in unrealized gains on assets still held at the reporting date $ 61.4 $ 46.5 $ 104.7 $ 91.1