Derivative Instruments (Details 1) (Foreign Exchange Contract [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
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)	$ 1.2	$ 16.0
Amount Reclassified from Accumulated Other Comprehensive Income into Income Gain/(Loss) (Effective Portion)	1.1	5.4
Other income (expense) [Member]
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Gains and losses in earnings of Foreign currency forward contracts due to hedge ineffectiveness	$ 0.2	$ 1.9