Debt - Credit Facility (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Line of Credit Facility [Line Items]
Receivables program maximum capacity	$ 105.0
Receivables facility amount outstanding	19.0	0
Receivables facility, letters credit outstanding	23.2
Receivables facility remaining borrowing capacity	62.8
Line of credit facility, amount outstanding	0
Line of credit facility, remaining borrowing capacity	$ 210.0
Accounts Receivable Facility, Renewal Term	364