Derivative Instruments (Details 1) (Foreign Exchange Contract, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue
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)	$ 6.8	$ (13.2)	$ 35.1
Other income (expense)
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Net gains (losses) in earnings of foreign currency forward contracts due to hedge ineffectiveness	$ (1.5)	$ (0.2)	$ 4.8