Financial Instruments - Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Foreign currency contracts | Prepayments and other current assets
Derivatives, Fair Value [Line Items]
Derivative assets	$ 6.3	$ 5.7
Foreign currency contracts | Other non-current assets
Derivatives, Fair Value [Line Items]
Derivative assets	0.1	0.2
Foreign currency contracts | Accounts payable and accrued expenses
Derivatives, Fair Value [Line Items]
Derivative liabilities	10.2	9.8
Foreign currency contracts | Other non-current liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	0.1	0
Net investment hedge contracts | Other non-current assets
Derivatives, Fair Value [Line Items]
Derivative assets	0	0
Net investment hedge contracts | Other non-current liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ 40.5	$ 58.1