Derivative Instruments (Details 1) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Amount Reclassified from Accumulated Other Comprehensive Income into Income Gain/(Loss) (Effective Portion)	$ (10.8)	$ 20.7	$ (37.6)	$ 40.6
Foreign Exchange Contract [Member] | Revenue [Member]
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Amount Recognized in Accumulated Other Comprehensive Income on Derivative Gain/(Loss) (Effective Portion )	13.5	(17.1)	13.5	(17.1)
Amount Reclassified from Accumulated Other Comprehensive Income into Income Gain/(Loss) (Effective Portion)	(10.8)	20.7	(37.6)	40.6
Foreign Exchange Contract [Member] | Other income (expense) [Member]
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Amount of Gain/(Loss) Recorded (Ineffective Portion )	$ (2.8)	$ 1.4	$ (3.2)	$ 0.9