Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Customer concentration Accounts receivable	Dec. 31, 2012 Customer concentration Accounts receivable	Dec. 31, 2013 Customer concentration Revenues.	Dec. 31, 2012 Customer concentration Revenues.	Dec. 31, 2011 Customer concentration Revenues.
Cash and Cash Equivalents
Maximum original term of maturities of cash and cash equivalents	3 months
Maximum term of maturities of time deposits	3 months
Restricted Cash
Maximum period until release for current restricted cash	1 year
Restricted Cash	$ 6.7	$ 7.6
Restricted Cash, non current	4.0	3.9
Concentration of Credit Risk
Allowance for doubtful accounts	$ 7.9	$ 7.9
Threshold for disclosure of risk concentrations (as a percent)			10.00%	10.00%	10.00%	10.00%	10.00%