Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivatives	$ 270.9	$ 282.0
Cash flow hedges [Member]
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivatives	117.1	137.6
Non-designated derivatives [Member]
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivatives	$ 153.8	$ 144.4