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Share-Based Compensation (Movements On Share Awards Priced In U.S. Dollars) (Details) (USD $)
In Millions, except Per Share data
9 Months Ended
Sep. 30, 2011
Sep. 30, 2010
Time Vested [Member]
  
Unvested at the beginning of period17.411.6
Granted during the period5.610.6
Forfeited during the period(0.3)(0.2)
Vested and distributed during the period(5.2)(3.1)
Unvested at the end of the period17.518.9
Weighted Average Grant Date Fair Value $ [Member]
  
Unvested at the beginning of period Weighted Average Grant Date Fair Value 17.25 15.24
Granted during period Weighted Average Grant Date Fair Value 26.74 19.13
Forfeited during period Weighted Average Grant Date Fair Value 19.36 18.81
Vested and distributed during the period Weighted Average Grant Date Fair Value 18.90 14.40
Unvested at the end of the period Weighted Average Grant Date Fair Value 20.25 17.52